OFFSET
1,2
PROG
(PARI) {a(n)=local(A=1+x); for(i=1, (n+2)^2+n+6, A=(1+x*A)*(1+x^(n+2)/(A+x*O(x^((n+2)^2+3))))); polcoeff(A, (n+2)^2+n+4)}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Nov 13 2011
STATUS
approved