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 A049737 #9 Aug 07 2021 01:12:17
%S A049737 1,17,49,125,213,361,433,617,805,1029,1345,1585,1801,2149,2461,2977,
%T A049737 3305,3709,4013,4557,5057,5689,6085,6661,7117,8025,8689,9205,10005,
%U A049737 10649,11281,12225,12941,13893,14449,15649,16297,17493
%N A049737 a(n) = Sum_{i=0..2n} (-1)^i * T(i,2n-i), array T as in A049735.
%K A049737 nonn
%O A049737 0,2
%A A049737 _Clark Kimberling_