OFFSET
0,4
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
FORMULA
From Seiichi Manyama, Feb 25 2022: (Start)
a(n) = n! * Sum_{k=0..floor(n/3)} (-1)^k * binomial(n-2*k,k)/(n-2*k)!.
a(n) = a(n-1) - 3! * binomial(n-1,2) * a(n-3) for n > 2. (End)
MATHEMATICA
Range[0, 24]! CoefficientList[Series[Exp[x - x^3], {x, 0, 24}], x] (* Robert G. Wilson v, Aug 31 2014, with correction from Vincenzo Librandi *)
PROG
(PARI) default(seriesprecision, 30); serlaplace(exp(x-x^3)) \\ Michel Marcus, Aug 31 2014
(PARI) a(n) = n!*sum(k=0, n\3, (-1)^k*binomial(n-2*k, k)/(n-2*k)!); \\ Seiichi Manyama, Feb 25 2022
(PARI) a(n) = if(n<3, 1, a(n-1)-3!*binomial(n-1, 2)*a(n-3)); \\ Seiichi Manyama, Feb 25 2022
CROSSREFS
KEYWORD
sign
AUTHOR
Robert G. Wilson v, Aug 31 2014
STATUS
approved