login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A095313
Primes in whose binary expansion the number of 1-bits is <= 6 + number of 0-bits.
4
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269
OFFSET
1,1
COMMENTS
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.
MATHEMATICA
Select[Prime[Range[100]], DigitCount[#, 2, 1]<= DigitCount[#, 2, 0]+6&] (* Harvey P. Dale, Aug 18 2016 *)
PROG
(PARI)forprime(p=2, 269, v=binary(p); s=0; for(k=1, #v, s+=if(v[k]==1, +1, -1)); if(s<=6, print1(p, ", "))) \\ Washington Bomfim, Jan 13 2011
CROSSREFS
Complement of A095312 in A000040. Subset: A095285, from which it differs first time at n=42, where a(42)=191 (10111111 in binary), while A095285(42)=193 (11000001 in binary). Cf. also A095333.
Sequence in context: A100725 A050260 A095316 * A095285 A163849 A124591
KEYWORD
nonn,base,easy
AUTHOR
Antti Karttunen, Jun 04 2004
STATUS
approved