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 A049647 #7 Aug 06 2021 05:09:11 %S A049647 1,1,4,4,7,7,11,11,17,17,23,23,31,31,41,41,51,51,61,61,75,75,89,89, %T A049647 105,105,123,123,137,137,153,153,177,177,199,199,223,223,249,249,269, %U A049647 269,291,291,323,323,353,353,381,381,413,413,443,443,473,473,513,513 %N A049647 a(n) = T(n,n+2), array T given by A049639. %K A049647 nonn %O A049647 0,3 %A A049647 _Clark Kimberling_ %E A049647 More terms from _Sean A. Irvine_, Aug 06 2021