OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} (-1)^k * binomial(n+1,k) * binomial(4*n-2*k+2,n-3*k).
PROG
(PARI) a(n) = sum(k=0, n\3, (-1)^k*binomial(n+1, k)*binomial(4*n-2*k+2, n-3*k))/(n+1);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Sep 28 2023
STATUS
approved