cp's OEIS Frontend

A158581 Numbers having in binary representation at least two ones and two zeros.

%I A158581 #22 Dec 24 2024 22:12:25
%S A158581 9,10,12,17,18,19,20,21,22,24,25,26,28,33,34,35,36,37,38,39,40,41,42,
%T A158581 43,44,45,46,48,49,50,51,52,53,54,56,57,58,60,65,66,67,68,69,70,71,72,
%U A158581 73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,96,97
%N A158581 Numbers having in binary representation at least two ones and two zeros.
%H A158581 Reinhard Zumkeller, <a href="/A158581/b158581.txt">Table of n, a(n) for n = 1..10000</a>
%F A158581 A023416(a(n)) > 1; A000120(a(n)) > 1.
%t A158581 Select[Range[100],Min[DigitCount[#,2]]>1&] (* _Harvey P. Dale_, Mar 09 2013 *)
%o A158581 (Python)
%o A158581 def ok(n): b = bin(n)[2:]; return b.count('0') >= 2 and b.count('1') >= 2
%o A158581 print(list(filter(ok, range(98)))) # _Michael S. Branicky_, Sep 10 2021
%o A158581 (Python)
%o A158581 def A158581(n):
%o A158581     def f(x):
%o A158581         c = n+((l:=(x+1).bit_length())*(l+1)>>1)-3
%o A158581         m = bin(x+1)[2:].find('0')
%o A158581         c += m if m>-1 else l
%o A158581         return c
%o A158581     m, k = n, f(n)
%o A158581     while m != k: m, k = k, f(k)
%o A158581     return m # _Chai Wah Wu_, Dec 24 2024
%Y A158581 Intersection of A158582 and A057716.
%Y A158581 Cf. A007088, A000120, A023416
%K A158581 nonn,base
%O A158581 1,1
%A A158581 _Reinhard Zumkeller_, Apr 16 2009