A368837 - OEIS

A368837

a(n) = n! * (n+2)! * Sum_{k=0..n} 1/(k! * (k+2)!).

1, 4, 33, 496, 11905, 416676, 20000449, 1260028288, 100802263041, 9979424041060, 1197530884927201, 171246916544589744, 28769481979491076993, 5610048986000760013636, 1256650972864170243054465, 320445998080363411978888576

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

Table of n, a(n) for n=0..15.

FORMULA

a(n) = n*(n+2)*a(n-1) + 1.

a(n) ~ BesselI(2,2) * n! * (n+2)!. - Vaclav Kotesovec, Jan 09 2024

PROG

(PARI) a(n) = n!*(n+2)!*sum(k=0, n, 1/(k!*(k+2)!));

CROSSREFS

Cf. A099597, A006040, A228229, A368838.

Sequence in context: A002190 A101981 A002018 * A219504 A258180 A072754

Adjacent sequences: A368834 A368835 A368836 * A368838 A368839 A368840

KEYWORD

nonn,easy

AUTHOR

Seiichi Manyama, Jan 07 2024

STATUS

approved