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 A114149 #11 Jun 15 2021 11:05:30 %S A114149 1,2,3,4,6,7,8,10,12,13,14,16,18,20,21,22,24,26,28,30,32,33,34,36,38, %T A114149 40,42,44,46,47,48,50,52,54,56,58,60,62,63,64,66,68,70,72,74,76,78,80, %U A114149 82,83,84,86,88,90,92,94,96,98,100,102,104,106,107,108,110,112,114,116,118 %N A114149 Self-describing sequence: 1 even integer between two odd, then 2 even integers between two odd, then 3 even integers, then 4, then 6... The length of each run of even integers is given by the sequence itself (the smallest odd available integer is used when needed). %e A114149 Runs of even integers are between brackets: %e A114149 1,(2),3,(4,6),7,(8,10,12),13,(14,16,18,20),21,(22,24,26,28,30,32),33... %e A114149 1 even 2 even 3 even 4 even 6 even... etc. = the sequence itself %K A114149 base,easy,nonn %O A114149 1,2 %A A114149 _Eric Angelini_ and _Alexandre Wajnberg_, Feb 03 2006