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 A131403 #9 Nov 22 2021 15:16:47
%S A131403 1,2,5,10,21,44,93,196,411,856,1771,3642,7451,15178,30809,62358,
%T A131403 125921,253800,510777,1026704,2061751,4137012,8295895,16627190,
%U A131403 33311671,66716054,133582133,267407026,535206861,1071049316,2143127061,4287918172,8578528851,17161414288
%N A131403 Row sums of triangle A131402.
%H A131403 Andrew Howroyd, <a href="/A131403/b131403.txt">Table of n, a(n) for n = 0..500</a>
%H A131403 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5, -8, 3, 3, -2)
%F A131403 From _Andrew Howroyd_, Aug 09 2018: (Start)
%F A131403 a(n) = 5*a(n-1) - 8*a(n-2) + 3*a(n-3) + 3*a(n-4) - 2*a(n-5).
%F A131403 G.f.: (1 - 3*x + 3*x^2 - 2*x^3 + 2*x^4)/((1 - x)^2*(1 - 2*x)*(1 - x - x^2)).
%F A131403 (End)
%e A131403 a(4) = 21 = sum of row 4 terms of A131402: (1 + 6 + 7 + 6 + 1).
%t A131403 LinearRecurrence[{5,-8,3,3,-2},{1,2,5,10,21},40] (* _Harvey P. Dale_, Nov 22 2021 *)
%o A131403 (PARI) Vec((1 - 3*x + 3*x^2 - 2*x^3 + 2*x^4)/((1 - x)^2*(1 - 2*x)*(1 - x - x^2)) + O(x^40)) \\ _Andrew Howroyd_, Aug 09 2018
%Y A131403 Cf. A131402.
%K A131403 nonn
%O A131403 0,2
%A A131403 _Gary W. Adamson_, Jul 07 2007
%E A131403 Terms a(10) and beyond from _Andrew Howroyd_, Aug 09 2018