OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n} (2*(n + k) - 1)!! / (2*(n - k) - 1)!!. - Detlef Meya, Oct 09 2023
a(n) ~ 2^(4*n + 1/2) * n^(2*n) / exp(2*n). - Vaclav Kotesovec, Oct 09 2023
MATHEMATICA
a[n_]:= Sum[(2*(n+k)-1)!!/(2*(n-k)-1)!!, {k, 0, n}]; Flatten[Table[a[n], {n, 0, 13}]] (* Detlef Meya, Oct 09 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, May 05 2023
STATUS
approved