OFFSET
0,2
REFERENCES
A. M. Gleason et al., The William Lowell Putnam Mathematical Competition: Problems and Solutions 1938-1964, Math. Assoc. America, 1980, p. 115.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (9,-27,27).
FORMULA
G.f.: (1 - 3*x + 18*x^2)/(1-3*x)^3. - Colin Barker, Jan 12 2012
MATHEMATICA
CoefficientList[Series[(1-3*x+18*x^2)/(1-3*x)^3, {x, 0, 30}], x] (* Vincenzo Librandi, Apr 16 2012 *)
PROG
(Magma)[(n^2+1)*3^n: n in [0..25]]; // Vincenzo Librandi, Apr 16 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved