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 A131615 #11 Sep 08 2022 08:45:31 %S A131615 0,1,2,4,5,8,9,10,12,13,17,21,22,24,26,30,32,33,36,42,46,66,101 %N A131615 Numbers k such that the decimal expansion of 3^k contains no 7. %C A131615 I conjecture that 101 is the last term. %t A131615 Select[ Range@10000, FreeQ[ IntegerDigits[3^# ],7] &] %o A131615 (Magma) [n: n in [0..1000] | not 7 in Intseq(3^n)]; // _Vincenzo Librandi_, May 06 2015 %Y A131615 Cf. similar sequences listed in A131613. %Y A131615 Cf. A007377. %K A131615 base,fini,nonn %O A131615 1,3 %A A131615 _Shyam Sunder Gupta_, Sep 01 2007 %E A131615 Initial 0 added and Mathematica code adapted by _Vincenzo Librandi_, May 06 2015