OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n} binomial(n+3*k+1,4*k+1) * binomial(3*k,k) / (2*k+1).
PROG
(PARI) a(n) = sum(k=0, n, binomial(n+3*k+1, 4*k+1)*binomial(3*k, k)/(2*k+1));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Jul 30 2023
STATUS
approved