OFFSET
0,3
FORMULA
a(n) = [x^n] n*x/((1-x) * (1-n*x)^3).
a(n) = n * (n^n * (n^4-n^3-3*n^2+3*n+2) - 2)/(2 * (n-1)^3) for n > 1.
PROG
(PARI) a(n) = sum(k=1, n, binomial(k+1, 2)*n^k);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Dec 29 2023
STATUS
approved