OFFSET
0,2
FORMULA
G.f.: 2*(1+x) / (1 + sqrt(1-4*x*(1+x)^5)).
a(n) = Sum_{k=0..n} binomial(5*k+1,n-k) * binomial(2*k,k)/(k+1).
PROG
(PARI) a(n) = sum(k=0, n, binomial(5*k+1, n-k)*binomial(2*k, k)/(k+1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Oct 05 2023
STATUS
approved