A095285 - OEIS

%I #12 Mar 03 2015 01:02:55

%S 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 97,101,103,107,109,113,131,137,139,149,151,157,163,167,173,179,181,

%U 193,197,199,211,227,229,233,241,257,263,269,271,277,281,283

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

%C 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 A. Karttunen and J. Moyer: <a href="/A095062/a095062.c.txt">C-program for computing the initial terms of this sequence</a>

%o (PARI) B(x) = { nB = floor(log(x)/log(2)); b1 = 0; b0 = 0;

%o for(i = 0, nB, if(bittest(x,i), b1++;, b0++;); );

%o if(b1 <= (5+b0), return(1);, return(0););};

%o forprime(x = 2, 283, if(B(x), print1(x, ", "); ); );

%o \\ _Washington Bomfim_, Jan 12 2011

%Y 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 nonn,base

%O 1,1

%A _Antti Karttunen_, Jun 04 2004