OFFSET
0,2
COMMENTS
Equals one-half of column 0 of A107719 shift 1 place left.
PROG
(PARI) {a(n)=if(n<0, 0, (matrix(n+2, n+2, m, j, if(m>=j, if(m==j, 1, if(m==j+1, -3*j, polcoeff(1/sum(i=0, m-j, prod(r=0, i-1, 3*r+1)*x^i)+O(x^m), m-j)))))^-1)[n+2, 2])}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 30 2005
STATUS
approved