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 A304272 #20 Jul 03 2021 07:58:06
%S A304272 2,21,212,2122,21221,212211,2122111,21221112,212211122,2122111221,
%T A304272 21221112212,212211122121,2122111221211,21221112212112,
%U A304272 212211122121122,2122111221211221,21221112212112212,212211122121122121,2122111221211221212,21221112212112212121,212211122121122121211,2122111221211221212112
%N A304272 The largest even integer that can be written with n digits in base 3/2.
%C A304272 a(n) is a prefix of a(n+1).
%C A304272 The largest, not necessarily even, integer in base 3/2 with n digits is a(n-1) with 2 added at the end.
%H A304272 B. Chen, R. Chen, J. Guo, S. Lee et al., <a href="http://arxiv.org/abs/1808.04304">On Base 3/2 and its Sequences</a>, arXiv:1808.04304 [math.NT], 2018.
%e A304272 The number 4 in base 3/2 is 21, and number 6 is 210. Therefore, 21 is the largest even integer with 2 digits in base 3/2.
%t A304272 Table[StringTake["212211122121122121211221211212112", n], {n, 32}]
%Y A304272 Cf. A304024, A304025, A070885, A303500, A024629, A081848, A246435, A005428, A073941.
%K A304272 nonn,base
%O A304272 1,1
%A A304272 _Tanya Khovanova_ and PRIMES STEP Senior group, May 09 2018