The On-Line Encyclopedia of Integer Sequences (OEIS)

A125800 revision #23

A125800

Rectangular table where column k equals row sums of matrix power A078122^k, read by antidiagonals.

1, 1, 1, 1, 2, 1, 1, 5, 3, 1, 1, 23, 12, 4, 1, 1, 239, 93, 22, 5, 1, 1, 5828, 1632, 238, 35, 6, 1, 1, 342383, 68457, 5827, 485, 51, 7, 1, 1, 50110484, 7112055, 342382, 15200, 861, 70, 8, 1, 1, 18757984046, 1879090014, 50110483, 1144664, 32856, 1393, 92, 9, 1

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OFFSET

0,5

COMMENTS

Determinant of n X n upper left submatrix is 3^(n*(n-1)*(n-2)/6).

This table is related to partitions of numbers into powers of 3 (see A078122).

Triangle A078122 shifts left one column under matrix cube.

Column 1 is A078125, which equals row sums of A078122;

column 2 is A078124, which equals row sums of A078122^2.

LINKS

Table of n, a(n) for n=0..54.

Robert Israel, Table of n, a(n) for n = 0..2484 (antidiagonals 0 to 69, flattened)

FORMULA

T(n,k) = T(n,k-1) + T(n-1,3*k) for n > 0, k > 0, with T(0,n)=T(n,0)=1 for n >= 0.

G.f. of row n is g_n(z) where g_{n+1}(z) = (1-z)^(-1)*Sum_{w^3=1} g_n(w*z^(1/3)) (the sum being over the cube roots of unity). - Robert Israel, Jun 02 2019

EXAMPLE

Recurrence T(n,k) = T(n,k-1) + T(n-1,3*k) is illustrated by:

T(3,3) = T(3,2) + T(2,9) = 93 + 145 = 238;

T(4,3) = T(4,2) + T(3,9) = 1632 + 4195 = 5827;

T(5,3) = T(5,2) + T(4,9) = 68457 + 273925 = 342382.

Rows of this table begin:

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...;

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, ...;

1, 5, 12, 22, 35, 51, 70, 92, 117, 145, 176, 210, ...;

1, 23, 93, 238, 485, 861, 1393, 2108, 3033, 4195, 5621, ...;

1, 239, 1632, 5827, 15200, 32856, 62629, 109082, 177507, 273925,...;

1, 5828, 68457, 342382, 1144664, 3013980, 6769672, 13570796, ...;

1, 342383, 7112055, 50110483, 215155493, 690729981, 1828979530, ...;

1, 50110484, 1879090014, 18757984045, 103674882878, 406279238154,..;

1, 18757984046, 1287814075131, 18318289003447, 130648799730635, ...;

Triangle A078122 begins:

1, 1;

1, 3, 1;

1, 12, 9, 1;

1, 93, 117, 27, 1;

1, 1632, 3033, 1080, 81, 1;

1, 68457, 177507, 86373, 9801, 243, 1; ...

where row sums form column 1 of this table A125790,

and column k of A078122 equals column 3^k - 1 of this table A125800.

Matrix square A078122^2 begins:

2, 1;

5, 6, 1;

23, 51, 18, 1;

239, 861, 477, 54, 1;

5828, 32856, 25263, 4347, 162, 1; ...

where row sums form column 2 of this table A125790,

and column 0 of A078122^2 forms column 1 of this table A125790.

MAPLE

f[0]:= 1/(1-z):

S[0]:= series(f[0], z, 21):

for n from 1 to 20 do

ff:= unapply(f[n-1], z);

f[n]:= simplify(1/3*sum(ff(w*z^(1/3)), w=RootOf(Z^3-1, Z)))/(1-z);

S[n]:= series(f[n], z, 21-n)

od:

seq(seq(coeff(S[s-i], z, i), i=0..s), s=0..20); # Robert Israel, Jun 02 2019

MATHEMATICA

T[0, _] = T[_, 0] = 1; T[n_, k_] := T[n, k] = T[n, k-1] + T[n-1, 3 k]; Table[T[n-k, k], {n, 0, 9}, {k, 0, n}] // Flatten (* Jean-François Alcover, Jan 08 2016 *)

PROG

(PARI) T(n, k, p=0, q=3)=local(A=Mat(1), B); if(n<p || p<0, 0, for(m=1, n+1, B=matrix(m, m); for(i=1, m, for(j=1, i, if(j==i || j==1, B[i, j]=1, B[i, j]=(A^q)[i-1, j-1]); )); A=B); return((A^(k+1))[n+1, p+1]))

CROSSREFS

Cf. A078122; columns: A078125, A078124, A125801, A125802, A125803; A125804 (diagonal), A125805 (antidiagonal sums); related table: A125800 (q=2).

Sequence in context: A294585 A283674 A294758 * A264698 A263296 A259862

Adjacent sequences: A125797 A125798 A125799 * A125801 A125802 A125803

KEYWORD

nonn,tabl,look

AUTHOR

Paul D. Hanna, Dec 10 2006

STATUS

proposed