This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A166380 #8 Jul 20 2019 08:03:20
%S A166380 1,3,19,223,4667,160045,8207125,587420875,55869454855,6809387511403,
%T A166380 1034264079708019,191477762192490649,42435372869814513769,
%U A166380 11090351278621719882899,3374951549996881393302715
%N A166380 Diagonal sums of exponential Riordan array [1+x^2*sec(x),x], A166378.
%F A166380 a(n) = Sum_{k=0..n} C(n+k,2k)*A166377(k).
%t A166380 (* The function RiordanArray is defined in A256893. *)
%t A166380 nmax = 14; R = RiordanArray[1 + #^2 Sec[#]&, #&, 2 nmax + 1, True];
%t A166380 a[n_] := Sum[R[[i, 2 n - i + 2]], {i, 2 n + 1, n + 1, -1}];
%t A166380 Table[a[n], {n, 0, nmax}] (* _Jean-François Alcover_, Jul 20 2019 *)
%Y A166380 Cf. A166377, A166378.
%K A166380 easy,nonn
%O A166380 0,2
%A A166380 _Paul Barry_, Oct 13 2009