OFFSET
0,2
COMMENTS
Sum of n-th hendecagonal number and n-th dodecagonal number.
Sum of reciprocals of a(n), for n>0: 0.59314195720519963010713286193275...
LINKS
Bruno Berselli, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
G.f.: x*(2+17*x)/(1-x)^3.
MATHEMATICA
Table[n (19 n - 15)/2, {n, 0, 50}]
CoefficientList[Series[x (2 + 17 x) / (1 - x)^3, {x, 0, 45}], x] (* Vincenzo Librandi, Aug 18 2013 *)
LinearRecurrence[{3, -3, 1}, {0, 2, 23}, 50] (* Harvey P. Dale, Aug 17 2017 *)
PROG
(Magma) [n*(19*n-15)/2: n in [0..50]];
(Magma) I:=[0, 2, 23]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+Self(n-3): n in [1..45]]; // Vincenzo Librandi, Aug 18 2013
(PARI) a(n)=n*(19*n-15)/2 \\ Charles R Greathouse IV, Jun 17 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Bruno Berselli, Jun 09 2013
STATUS
approved