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 A131625 #18 Jun 08 2025 03:34:43
%S A131625 0,1,2,4,8,9,10,11,12,15,20,22,29,34,35,54,59
%N A131625 Numbers k such that decimal expansion of 3^k contains no 2.
%C A131625 I conjecture that 59 is the last term.
%t A131625 Join[{0}, Select[ Range@10000, FreeQ[ IntegerDigits[3^# ], 2] &]]
%o A131625 (Magma) [n: n in [0..1000] | not 2 in Intseq(3^n)]; // _Vincenzo Librandi_, May 06 2015
%o A131625 (PARI) isok(n) = ! vecsearch(Set(digits(3^n)), 2); \\ _Michel Marcus_, Feb 09 2018
%Y A131625 Cf. similar sequences listed in A131613.
%Y A131625 Cf. A007377.
%K A131625 base,fini,nonn,more
%O A131625 1,3
%A A131625 _Shyam Sunder Gupta_, Sep 01 2007
%E A131625 Initial 0 added and Mathematica code adapted by _Vincenzo Librandi_, May 06 2015