OFFSET
0,2
LINKS
FORMULA
E.g.f.: exp(-x/(1-x))/(1-x)^3.
a(n) = Sum_{m=0..n} ((-1)^m)*n!*binomial(n+2, n-m)/m!.
a(n) = 2*n*a(n-1) - (n-1)*(n+1)*a(n-2). - Vaclav Kotesovec, Aug 01 2013
a(n) = (n+2)!*hypergeom([-n],[3],1)/2. - Peter Luschny, Apr 11 2015
MAPLE
a := n -> (n+2)!*hypergeom([-n], [3], 1)/2:
seq(simplify(a(n)), n=0..20); # Peter Luschny, Apr 11 2015
MATHEMATICA
Table[n!*LaguerreL[n, 2, 1], {n, 0, 20}] (* Vaclav Kotesovec, Aug 01 2013 *)
PROG
(PARI) for(n=0, 30, print1(n!*sum(k=0, n, (-1)^k*binomial(n+2, n-k)/k!), ", ")) \\ G. C. Greubel, May 13 2018
(PARI) a(n) = vecsum(Vec(n!*pollaguerre(n, 2))); \\ Michel Marcus, Feb 06 2021
(Magma) [Factorial(n)*(&+[(-1)^k*Binomial(n+2, n-k)/Factorial(k): k in [0..n]]): n in [0..30]]; // G. C. Greubel, May 13 2018
CROSSREFS
KEYWORD
sign,easy
AUTHOR
Wolfdieter Lang, Jun 19 2001
STATUS
approved