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 A370919 #7 Mar 17 2024 04:07:49
%S A370919 5,15,17,23,45,47,50,51,53,59,69,71,77,135,137,140,141,143,150,152,
%T A370919 153,155,158,159,161,167,177,179,185,207,209,212,213,215,221,231,233,
%U A370919 239,405,407,410,411,413,420,422,423,425,428,429,431,450,452,455,456
%N A370919 Positive integers whose ternary representation includes at least one 1, and every 1 is followed by 2.
%e A370919 The ternary representations of 5, 15, and 17 are 12, 120, and 122.
%t A370919 Map[#[[1]] &, Select[Map[{#, #[[1]] > 0 && #[[1]] == #[[2]] &[{Length[
%t A370919 StringCases[#, "1"]], Length[StringCases[#, "12"]]}] &[
%t A370919 IntegerString[#, 3]]} &, Range[500]], #[[2]] &]] (* _Peter J. C. Moses_, Mar 05 2024 *)
%Y A370919 Cf. A007089, A081606.
%Y A370919 Cf. A370916, A370917, A370918, A370920, A370921, A370922, A370923.
%K A370919 nonn,base
%O A370919 1,1
%A A370919 _Clark Kimberling_, Mar 16 2024