OFFSET
0,3
MATHEMATICA
a[n_] := Sum[If[n == 0, Boole[n == k], (-n)^(n - k)] * Binomial[2*k, k] * Binomial[2*n, 2*k], {k, 0, n}]; Array[a, 20, 0] (* Amiram Eldar, Aug 27 2020 *)
PROG
(PARI) {a(n) = sum(k=0, n, (-n)^(n-k)*binomial(2*k, k)*binomial(2*n, 2*k))}
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Aug 27 2020
STATUS
approved