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 A131618 #12 Jun 08 2025 03:34:47
%S A131618 0,1,2,3,4,6,7,8,9,22,33,34,38,46,49,75,106
%N A131618 Numbers k such that the decimal expansion of 3^k contains no 4.
%C A131618 I conjecture that 106 is the last term.
%t A131618 Join[{0}, Select[ Range@10000, FreeQ[ IntegerDigits[3^# ], 4] &]]
%o A131618 (Magma) [n: n in [0..1000] | not 4 in Intseq(3^n)]; // _Vincenzo Librandi_, May 06 2015
%Y A131618 Cf. similar sequences listed in A131613.
%Y A131618 Cf. A007377.
%K A131618 base,fini,nonn
%O A131618 1,3
%A A131618 _Shyam Sunder Gupta_, Sep 01 2007
%E A131618 Initial 0 added and Mathematica code adapted by _Vincenzo Librandi_, May 06 2015