OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n} binomial(4*(n-k)+2,k) * binomial(k,n-k)/(2*(n-k)+1).
G.f.: A(x) = B(x)^2 where B(x) is the g.f. of A137954.
PROG
(PARI) a(n, r=2, s=1, t=0, u=4) = r*sum(k=0, n, binomial(t*k+u*(n-k)+r, k)*binomial(s*k, n-k)/(t*k+u*(n-k)+r));
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Mar 29 2024
STATUS
approved