OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..695
Index entries for linear recurrences with constant coefficients, signature (40,-390,1080,-729).
FORMULA
a(n) = (3^n - 1)*(3^n + 1)^2/32.
From G. C. Greubel, May 22 2023: (Start)
G.f.: x*(1 -15*x +27*x^2)/((1-x)*(1-3*x)*(1-9*x)*(1-27*x)).
E.g.f.: (1/32)*(- exp(x) - exp(3*x) + exp(9*x) + exp(27*x)). (End)
MATHEMATICA
Table[(9^n-1)*(3^n+1)/32, {n, 0, 30}]
PROG
(Magma) [(9^n-1)*(3^n+1)/32: n in [0..40]]; // G. C. Greubel, May 22 2023
(SageMath) [(9^n-1)*(3^n+1)/32 for n in range(41)] # G. C. Greubel, May 22 2023
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Dec 01 2008
STATUS
approved