OFFSET
0,3
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..50
N. J. A. Sloane, Transforms
FORMULA
a(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n, k)*2^(k*(k-1)).
EXAMPLE
2^(n*(n-1))=1+3*C(n,2)+54*C(n,3)+3861*C(n,4)+...
MATHEMATICA
nn=20; s=Sum[2^(2Binomial[n, 2])x^n/n!, {n, 0, nn}]; Range[0, nn]!CoefficientList[Series[ s/Exp[x], {x, 0, nn}], x] (* Geoffrey Critzer, Oct 07 2012 *)
PROG
(PARI) a(n)={sum(k=0, n, (-1)^(n-k)*binomial(n, k)*2^(k*(k-1)))} \\ Andrew Howroyd, Nov 07 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Vladeta Jovovic, Apr 09 2000
EXTENSIONS
Terms a(12) and beyond from Andrew Howroyd, Nov 07 2019
STATUS
approved