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 A321574 #14 Feb 05 2020 05:34:14
%S A321574 1,4,20,108,604,3444,19876,115644,676748,3977316,23451700,138634764,
%T A321574 821221692,4872734676,28952250564,172222729308,1025461169772,
%U A321574 6110912705220,36441840179284,217450403367852,1298228971572764,7754336590794804,46335720234364900
%N A321574 Row sums of A321623.
%F A321574 G.f.: 1/(sqrt(1 - 6*x + x^2) - x). - _Philippe Deléham_, Feb 05 2020
%t A321574 (* The function RiordanSquare is defined in A321620. *)
%t A321574 LargeSchröder = (1 - x - Sqrt[1 - 6x + x^2])/(2x);
%t A321574 M = RiordanSquare[LargeSchröder, 23]; Map[Total, M]
%t A321574 (* Alternative: *)
%t A321574 CoefficientList[Series[1/(Sqrt[1-6x+x^2]-x),{x,0,22}],x] (* _Stefano Spezia_, Feb 05 2020 *)
%Y A321574 Cf. A321623, A321620.
%K A321574 nonn
%O A321574 0,2
%A A321574 _Peter Luschny_, Nov 22 2018