Search: a288834 -id:a288834
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A066373
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a(n) = (3*n-2)*2^(n-3).
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+10
7
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2, 7, 20, 52, 128, 304, 704, 1600, 3584, 7936, 17408, 37888, 81920, 176128, 376832, 802816, 1703936, 3604480, 7602176, 15990784, 33554432, 70254592, 146800640, 306184192, 637534208, 1325400064, 2751463424, 5704253440
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OFFSET
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2,1
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COMMENTS
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An elephant sequence, see A175654. For the corner squares 16 A[5] vectors, with decimal values between 59 and 440, lead to this sequence (with a leading 1 added). For the central square these vectors lead to the companion sequence A098156 (without a(1)). - Johannes W. Meijer, Aug 15 2010
a(n) is the total number of 1's in runs of 1's of length >= 2 over all binary words with n bits. - Félix Balado, Jan 15 2024
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LINKS
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FORMULA
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Inverse binomial transform of A288834.
Also the main diagonal of the difference table of m -> (-1)^m*(m+2).
2, -3, 4, -5, ...
-5, 7, -9, 11, ...
12, -16, 20, -24, ...
-28, 36, -44, 52, ... . (End)
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MAPLE
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MATHEMATICA
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Array[(3 # - 2)*2^(# - 3) &, 28, 2] (* or *)
Drop[CoefficientList[Series[x^2*(2 - x)/(1 - 2 x)^2, {x, 0, 29}], x], 2] (* Michael De Vlieger, Jun 30 2018 *)
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PROG
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(PARI) { for (n=2, 200, write("b066373.txt", n, " ", (3*n - 2)*2^(n - 3)) ) } /* Harry J. Smith, Feb 11 2010 */
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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A080420
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a(n) = (n+1)*(n+6)*3^n/6.
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+10
7
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1, 7, 36, 162, 675, 2673, 10206, 37908, 137781, 492075, 1732104, 6022998, 20726199, 70681653, 239148450, 803538792, 2683245609, 8910671247, 29443957164, 96855122250, 317297380491, 1035574967097, 3368233731366, 10920608743932, 35303692060125, 113819103201843
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: (1-2*x)/(1-3*x)^3.
a(n) = (n+6)*A288834(n)/2, for n >= 1.
E.g.f.: (1/2)*(2 + 8*x + 3*x^2)*exp(3*x). (End)
Sum_{n>=0} 1/a(n) = 17721/50 - 4356*log(3/2)/5.
Sum_{n>=0} (-1)^n/a(n) = 4392*log(4/3)/5 - 12591/50. (End)
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MATHEMATICA
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CoefficientList[Series[(1 - 2 x) / (1 - 3 x)^3, {x, 0, 30}], x] (* Vincenzo Librandi, Aug 05 2013 *)
Table[(n+1)(n+6)3^n/6, {n, 0, 30}] (* or *) LinearRecurrence[{9, -27, 27}, {1, 7, 36}, 30] (* Harvey P. Dale, Apr 02 2019 *)
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PROG
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(SageMath) [(n+1)*(n+6)*3^n/6 for n in range(31)] # G. C. Greubel, Dec 22 2023
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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A288836
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a(n) = (1/3!)*3^(n+1)*(n+5)*(n+1)*(n).
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+10
4
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18, 189, 1296, 7290, 36450, 168399, 734832, 3070548, 12400290, 48715425, 187067232, 704690766, 2611501074, 9542023155, 34437376800, 122941435176, 434685788658, 1523724783237, 5299912289520, 18305618105250, 62824881337218, 214364018189079, 727538485975056
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OFFSET
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1,1
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LINKS
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FORMULA
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O.g.f.: z*3^2*(2-3*z)/(1-3*z)^4.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A288835
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a(n) = (1/2!)*3^n*(n+3)*(n).
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+10
3
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6, 45, 243, 1134, 4860, 19683, 76545, 288684, 1062882, 3838185, 13640319, 47829690, 165809592, 569173311, 1937102445, 6543101592, 21953827710, 73222472421, 242912646603, 801960412230, 2636009007156, 8629791392475, 28148810469273, 91507169819844
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OFFSET
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1,1
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LINKS
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FORMULA
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O.g.f.: z*3^1*(2-3*z)/(1-3*z)^3.
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MATHEMATICA
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LinearRecurrence[{9, -27, 27}, {6, 45, 243}, 30] (* Harvey P. Dale, Apr 04 2020 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A288838
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a(n) = (1/4!)*3^(n+2)*(n+7)*(n+2)*(n+1)*(n).
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+10
3
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54, 729, 6075, 40095, 229635, 1194102, 5786802, 26572050, 116917020, 496897335, 2051893701, 8269753401, 32643763425, 126557359740, 482984209620, 1817776934388, 6757388169138, 24843338857125, 90429753439935, 326206114635555, 1167092987918319, 4144371018322194
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OFFSET
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1,1
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LINKS
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FORMULA
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O.g.f.: z*3^3*(2-3*z)/(1-3*z)^5.
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MATHEMATICA
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Table[1/4! 3^(n+2) (n+7)(n+2)(n+1)n, {n, 30}] (* or *) LinearRecurrence[{15, -90, 270, -405, 243}, {54, 729, 6075, 40095, 229635}, 30] (* Harvey P. Dale, May 15 2022 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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A354314
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Expansion of e.g.f. 1/(1 - x/3 * (exp(3 * x) - 1)).
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+10
2
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1, 0, 2, 9, 60, 495, 4986, 58401, 780984, 11749779, 196446870, 3612882933, 72484364052, 1575418827879, 36875093680530, 924769734574185, 24737895033896304, 703105981990977915, 21159355356941587470, 672148402091190649629, 22475238194908656800460
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OFFSET
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0,3
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LINKS
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FORMULA
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a(0) = 1; a(n) = Sum_{k=2..n} k * 3^(k-2) * binomial(n,k) * a(n-k).
a(n) = n! * Sum_{k=0..floor(n/2)} 3^(n-2*k) * k! * Stirling2(n-k,k)/(n-k)!.
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PROG
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(PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(1/(1-x/3*(exp(3*x)-1))))
(PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=sum(j=2, i, j*3^(j-2)*binomial(i, j)*v[i-j+1])); v;
(PARI) a(n) = n!*sum(k=0, n\2, 3^(n-2*k)*k!*stirling(n-k, k, 2)/(n-k)!);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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A288842
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Triangle (sans apex) of coefficients of terms of the form (eM_1)^j*(eM_2)^k re construction of triangle A287768.
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+10
0
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1, 2, 3, 9, 6, 9, 36, 45, 18, 27, 135, 243, 189, 54, 81, 486, 1134, 1296, 729, 162, 243, 1701, 4860, 7290, 6075, 2673, 486, 729, 5832, 19683, 36450, 40095, 26244, 9477, 1458, 2187, 19683, 76545, 168399, 229635, 199017, 107163, 32805, 4374, 6561, 65610, 288684, 734832, 1194102, 1285956, 918540, 419904, 111537, 13122
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OFFSET
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1,2
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LINKS
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FORMULA
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T(n+1,k+1) = 3*T(n,k) + 3*T(n,k+1).
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EXAMPLE
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Triangle begins:
1, 2;
3, 9, 6;
9, 36, 45, 18;
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MATHEMATICA
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T[1, 1] = 1; T[1, 2] = 2;
T[n_, k_] /; 1 <= k <= n+1 := T[n, k] = 3 T[n-1, k-1] + 3 T[n-1, k];
T[_, _] = 0;
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CROSSREFS
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KEYWORD
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nonn,tabf
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AUTHOR
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STATUS
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approved
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