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 A131270 #10 Feb 18 2022 22:33:58
%S A131270 1,1,1,1,1,1,1,3,1,1,1,3,5,1,1,1,5,5,7,1,1,1,5,11,7,9,1,1,1,7,11,19,9,
%T A131270 11,1,1,1,7,19,19,29,11,13,1,1,1,9,19,39,29,41,13,15,1,1,1,9,29,39,69,
%U A131270 41,55,15,17,1,1,1,11,29,69,69,111,55,71,17,19,1,1
%N A131270 Triangle T(n,k) = 2*A046854(n,k) - 1, read by rows.
%C A131270 Row sums = A131269: {1, 2, 3, 6, 11, 20, 35, 60, 101, 168, ...}.
%H A131270 G. C. Greubel, <a href="/A131270/b131270.txt">Rows n = 0..100 of triangle, flattened</a>
%F A131270 T(n,k) = 2*A046854(n,k) - 1.
%F A131270 Reversed triangle of A131268.
%e A131270 First few rows of the triangle:
%e A131270 1;
%e A131270 1, 1;
%e A131270 1, 1, 1;
%e A131270 1, 3, 1, 1;
%e A131270 1, 3, 5, 1, 1;
%e A131270 1, 5, 5, 7, 1, 1;
%e A131270 1, 5, 11, 7, 9, 1, 1;
%e A131270 1, 7, 11, 19, 9, 11, 1, 1;
%e A131270 ...
%t A131270 Table[2*Binomial[Floor[(n+k)/2], k] - 1, {n,0,12}, {k,0,n}]//Flatten (* _G. C. Greubel_, Jul 09 2019 *)
%o A131270 (PARI) T(n,k) = 2*binomial((n+k)\2, k)-1; \\ _G. C. Greubel_, Jul 09 2019
%o A131270 (Magma) [[2*Binomial(Floor((n+k)/2), k) -1: k in [0..n]]:n in [0..12]]; // _G. C. Greubel_, Jul 09 2019
%o A131270 (Sage) [[2*binomial(floor((n+k)/2), k) -1 for k in (0..n)] for n in (0..12)] # _G. C. Greubel_, Jul 09 2019
%Y A131270 Cf. A046854, A065941, A000012, A131268, A131269.
%K A131270 nonn,tabl
%O A131270 0,8
%A A131270 _Gary W. Adamson_, Jun 23 2007