cp's OEIS Frontend

A095285 Primes in whose binary expansion the number of 1 bits is <= 5 + number of 0 bits.

%I A095285 #12 Mar 03 2015 01:02:55
%S A095285 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,
%T A095285 97,101,103,107,109,113,131,137,139,149,151,157,163,167,173,179,181,
%U A095285 193,197,199,211,227,229,233,241,257,263,269,271,277,281,283
%N A095285 Primes in whose binary expansion the number of 1 bits is <= 5 + number of 0 bits.
%C A095285 Differs from primes (A000040) first time at n=31, where a(31)=131, while A000040(31)=127, as 127 whose binary expansion is 1111111, with 7 1-bits and no 0-bits is the first prime excluded from this sequence. Note that 63 (111111 in binary) is not prime.
%H A095285 A. Karttunen and J. Moyer: <a href="/A095062/a095062.c.txt">C-program for computing the initial terms of this sequence</a>
%o A095285 (PARI) B(x) = { nB = floor(log(x)/log(2)); b1 = 0; b0 = 0;
%o A095285 for(i = 0, nB, if(bittest(x,i), b1++;, b0++;); );
%o A095285 if(b1 <= (5+b0), return(1);, return(0););};
%o A095285 forprime(x = 2, 283, if(B(x), print1(x, ", "); ); );
%o A095285 \\ _Washington Bomfim_, Jan 12 2011
%Y A095285 Complement of A095284 in A000040. Subset: A095323. Subset of A095313, from which it differs first time at n=42, where a(42)=193 (11000001 in binary) while A095313(42)=191 (10111111 in binary). Cf. also A095286, A095295.
%K A095285 nonn,base
%O A095285 1,1
%A A095285 _Antti Karttunen_, Jun 04 2004