OFFSET
0,3
FORMULA
PROG
(PARI) {a(n)=local(p=2, A, C, X=x+x*O(x^(p*n))); if(n==0, 1, A=sum(i=0, n-1, a(i)*x^(p*i))+p*x*((1-x^(p-1))/(1-X))/(1-X^p); for(k=1, p, C=polcoeff((A+k*x^(p*n))^(1/p), p*n); if(denominator(C)==1, return(k); break)))}
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v and Paul D. Hanna, Aug 08 2005
STATUS
approved