OFFSET
0,3
FORMULA
a(n) = [x^n] x/((1-n*x) * (1-x)^3).
a(n) = n * (2*n^(n+1) - n^3 - n^2 + n - 1)/(2 * (n-1)^3) for n > 1.
PROG
(PARI) a(n) = sum(k=1, n, binomial(k+1, 2)*n^(n-k));
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Dec 29 2023
STATUS
approved