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 A176764 #13 Apr 03 2024 15:30:19
%S A176764 1024,1,256,16384,4,256,16,1048576,16384,4096,1024,1099511627776,
%T A176764 1125899906842624,1180591620717411303424,262144,288230376151711744,16,
%U A176764 17179869184,1073741824,4194304,72057594037927936,262144,4722366482869645213696
%N A176764 Smallest power of 4 whose decimal expansion contains n.
%C A176764 This is to 4 as A176763 is to 3 and as A030001 is to 2.
%H A176764 Paolo Xausa, <a href="/A176764/b176764.txt">Table of n, a(n) for n = 0..10000</a>
%F A176764 a(n) = MIN{A000302(i) such that n in decimal representation is a substring of A000302(i)}.
%F A176764 a(n) = 4^A062521(n). - _Michel Marcus_, Sep 30 2014
%e A176764 a(1) = 1 because 4^0 = 1 has "1" as a substring (not a proper substring, though).
%e A176764 a(2) = 256 because 4^4 = 256 has "2" as a substring.
%e A176764 a(3) = 16384 because 4^7 = 16384 has "3" as a substring.
%t A176764 A176764[n_] := Block[{k = -1}, While[StringFreeQ[IntegerString[4^++k], IntegerString[n]]]; 4^k]; Array[A176764, 50, 0] (* _Paolo Xausa_, Apr 03 2024 *)
%Y A176764 Cf. A000302, A030001, A176763, A176765-A176773.
%K A176764 base,easy,nonn
%O A176764 0,1
%A A176764 _Jonathan Vos Post_, Apr 25 2010
%E A176764 Corrected and extended by _Sean A. Irvine_ and _Jon E. Schoenfield_, May 05 2010
%E A176764 a(0) prepended by _Paolo Xausa_, Apr 03 2024