OFFSET
0,7
FORMULA
a(0) = 1; a(n) = -Sum_{k=0..floor((n-1)/5)} a(k) * a(n-5*k-1). - Ilya Gutkovskiy, Mar 01 2022
PROG
(PARI) a(n)=local(A); A=1-x; for(i=1, n\5+1, A=1/(1+x*subst(A, x, x^5)+x*O(x^n))); polcoeff(A, n, x)
(PARI) a(n)=local(M=contfracpnqn(concat(1, vector(ceil(log(n+1)/log(5))+1, n, 1/x^(5^(n-1)))))); polcoeff(M[1, 1]/M[2, 1]+x*O(x^(6*n+1)), 6*n+1)
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Dec 20 2004
STATUS
approved