OFFSET
6,1
LINKS
FORMULA
a(n)=n^n-6*(n-1)^n+15*(n-2)^n-20*(n-3)^n+15*(n-4)^n-6*(n-5)^n+(n-6)^n, (n=6,7,...)
EXAMPLE
a(7)=20160
MAPLE
a:=n->n^n-6*(n-1)^n+15*(n-2)^n-20*(n-3)^n+15*(n-4)^n-6*(n-5)^n+(n-6)^n;
MATHEMATICA
Drop[Table[Sum[(-1)^k Binomial[6, k] (n-k)^n, {k, 0, 6}], {n, 1, 20}], 5] (* Geoffrey Critzer, Dec 23 2012 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Aleksandar M. Janjic and Milan Janjic, Feb 18 2007
STATUS
approved