OFFSET
0,6
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..899
FORMULA
a(n) = (a(n-1) - n * a(n-2) + 1)/2 for n > 1.
MATHEMATICA
nxt[{n_, a_, b_}]:={n+1, b, (b-a(n+1)+1)/2}; NestList[nxt, {1, 1, 1}, 40][[;; , 2]] (* Harvey P. Dale, Jul 25 2024 *)
PROG
(PARI) a(n) = sum(k=0, n\2, (-1)^k*(n-k)!/(n-2*k)!);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Nov 23 2022
STATUS
approved