cp's OEIS Frontend

A063565 Smallest positive number k such that 2^k contains n.

%I A063565 #14 May 22 2025 10:21:34
%S A063565 10,4,1,5,2,8,4,15,3,12,10,40,7,17,18,21,4,27,30,13,11,18,43,41,10,8,
%T A063565 18,15,7,32,22,17,5,25,27,25,16,30,14,42,12,22,19,22,18,28,42,31,11,
%U A063565 32,52,9,19,16,25,16,8,20,33,33,23,58,18,14,6,16,46,24,15,34,29,21,17,30
%N A063565 Smallest positive number k such that 2^k contains n.
%H A063565 Chai Wah Wu, <a href="/A063565/b063565.txt">Table of n, a(n) for n = 0..10000</a>
%H A063565 Popular Computing (Calabasas, CA), <a href="/A094776/a094776.jpg">Two Tables</a>, Vol. 1, (No. 9, Dec 1973), page PC9-16.
%e A063565 a(7) = 15 because 2^15 = 32768.
%t A063565 a = {}; Do[k = 1; While[ StringPosition[ ToString[2^k], ToString[n] ] == {}, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
%o A063565 (Python)
%o A063565 def A063565(n):
%o A063565     s, k, k2 = str(n), 1, 2
%o A063565     while True:
%o A063565         if s in str(k2):
%o A063565             return k
%o A063565         k += 1
%o A063565         k2 *= 2 # _Chai Wah Wu_, Jun 20 2015
%Y A063565 Apart from initial term, a duplicate of A030000.
%Y A063565 Cf. A006889, A131535, A131536, A259089, A063565, A259091, A259092.
%K A063565 base,nonn
%O A063565 0,1
%A A063565 _Robert G. Wilson v_, Aug 10 2001
%E A063565 More terms from _Hans Havermann_