OFFSET
0,2
FORMULA
a(n) = Sum_{k=0..n} C(n+k,2k)*A166377(k).
MATHEMATICA
(* The function RiordanArray is defined in A256893. *)
nmax = 14; R = RiordanArray[1 + #^2 Sec[#]&, #&, 2 nmax + 1, True];
a[n_] := Sum[R[[i, 2 n - i + 2]], {i, 2 n + 1, n + 1, -1}];
Table[a[n], {n, 0, nmax}] (* Jean-François Alcover, Jul 20 2019 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Oct 13 2009
STATUS
approved