A235985 Primes p such that 3p-1 has even Hamming weight.

2, 7, 23, 29, 31, 71, 103, 107, 109, 113, 127, 151, 157, 167, 199, 227, 229, 233, 263, 283, 313, 347, 349, 359, 367, 373, 379, 383, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 541, 569, 599, 607, 619, 631, 647, 739, 761, 797

Offset: 1

Author

Juri-Stepan Gerasimov, Jan 17 2014

Keywords

• nonn
• base

Comments

Primes p such that A000120(3p-1) is even.

Smallest prime p such that A000120(np-1) is even: 7, 2, 2, 7, 5, 3, 3, 2, 2, 3, 5, 2, 7,...

Examples

			23 is in this sequence because A000120(3*23-1) = A000120(68) = 2 (even number).
29 is in this sequence because A000120(3*29-1) = A000120(86) = 4 (even number).
		

Crossrefs

Cf. A019434 (odd primes p having Hamming weight 2), A027697 (primes p having odd Hamming weight), A027699 (primes p having an even Hamming weight).

Programs

Mathematica

Select[Prime@Range@200, EvenQ@ First@ DigitCount[3#-1, 2] &] (* Giovanni Resta, Jan 26 2014 *)

PARI

isok(p) = isprime(p) && !(hammingweight(3*p-1) % 2); \\ Michel Marcus, Jan 18 2014