OFFSET
0,3
FORMULA
a(n) = [x^n] n*x * (1+n*x)/((1-x) * (1-n*x)^3).
a(n) = n * (n+1) * (n^n * (n^3-3*n^2+2*n+1) - 1)/(n-1)^3 for n > 1.
PROG
(PARI) a(n) = sum(k=1, n, k^2*n^k);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Dec 28 2023
STATUS
approved