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 A047131 #14 Jan 20 2020 01:33:05
%S A047131 1,2,3,6,10,20,35,70,140,252,504,932,1864,3493,6986,13972,26265,52530,
%T A047131 100168,200336,384573,769146,1538292,2950530,5901060,11422700,
%U A047131 22845400,44403564,88807128,177614256,344644881,689289762,1346117062
%N A047131 a(n) = Sum_{i=0..n} A047130(i, n-i).
%H A047131 Andrew Howroyd, <a href="/A047131/b047131.txt">Table of n, a(n) for n = 0..200</a>
%o A047131 (PARI) A(h, k=h)={my(M=matrix(h+1, k+1, i, j, 1)); for(h=1, h, for(k=1, k, M[1+h, 1+k] = M[h, 1+k] + if(4*k>3*h && 4*(k-1)<3*h, 0, M[1+h, k]))); M}
%o A047131 seq(n)={my(T=A(n)); vector(#T, k, sum(i=0, k-1, T[1+i, k-i]))} \\ _Andrew Howroyd_, Jan 19 2020
%Y A047131 Cf. A047130.
%K A047131 nonn
%O A047131 0,2
%A A047131 _Clark Kimberling_
%E A047131 Definition corrected and edited by _Georg Fischer_, Jan 19 2020