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 A063567 #14 May 02 2021 11:11:26
%S A063567 5,2,4,7,1,4,2,10,7,6,5,20,25,35,9,29,2,17,15,11,28,9,36,29,5,4,9,19,
%T A063567 24,16,11,37,38,43,35,14,8,15,7,21,6,11,16,11,9,14,21,18,10,16,26,20,
%U A063567 30,8,14,8,4,10,25,22,22,29,9,7,3,8,23,12,14,17,23,13
%N A063567 Smallest positive power of 4 having n in its decimal representation.
%t A063567 a = {}; Do[k = 1; While[ StringPosition[ ToString[4^k], ToString[n] ] == {}, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
%t A063567 sp4[n_]:=Module[{k=1,idn=IntegerDigits[n]},While[SequenceCount[ IntegerDigits[ 4^k], idn] == 0, k++];k]; Array[sp4,70,0] (* The program uses the SequenceCount function from Mathematica version 10 *) (* _Harvey P. Dale_, Mar 12 2016 *)
%o A063567 (Python)
%o A063567 def a(n):
%o A063567 target, k, pow4 = str(n), 1, 4
%o A063567 while not target in str(pow4): k, pow4 = k+1, pow4*4
%o A063567 return k
%o A063567 print([a(n) for n in range(72)]) # _Michael S. Branicky_, May 02 2021
%Y A063567 Essentially the same as A062521.
%K A063567 base,nonn
%O A063567 0,1
%A A063567 _Robert G. Wilson v_, Aug 10 2001
%E A063567 Name edited and more terms from _Michael S. Branicky_, May 02 2021