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 A049713 #8 Aug 07 2021 00:17:39
%S A049713 1,8,17,38,63,102,121,170,217,276,359,422,473,562,643,776,861,966,
%T A049713 1041,1176,1303,1468,1569,1712,1825,2056,2225,2358,2565,2722,2877,
%U A049713 3116,3301,3540,3681,3982,4145,4446,4631,4984,5161,5314
%N A049713 a(n) = Sum_{i=0..2n} (-1)^i * T(i,2n-i), array T as in A048149.
%K A049713 nonn
%O A049713 0,2
%A A049713 _Clark Kimberling_