OFFSET
1,4
COMMENTS
Equals the third column in triangle A104382.
FORMULA
a(n) = round((3n^4 + 6n^3 - 33n^2 - 36n + 110)/144) (conjectured). - Ralf Stephan, Nov 13 2010.
PROG
(PARI) {a(n)=if(n<1, 0, polcoeff(polcoeff( prod(i=1, n*(n+1)/2, 1+y*x^i, 1+x*O(x^(n*(n+1)/2))), n*(n+1)/2, x), 3, y))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 04 2005
STATUS
approved