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%I #21 Jan 27 2014 18:25:42
%S 2,7,23,29,31,71,103,107,109,113,127,151,157,167,199,227,229,233,263,
%T 283,313,347,349,359,367,373,379,383,431,433,439,443,449,457,461,463,
%U 467,479,487,491,499,503,509,541,569,599,607,619,631,647,739,761,797
%N Primes p such that 3p-1 has even Hamming weight.
%C Primes p such that A000120(3p-1) is even.
%C Smallest prime p such that A000120(np-1) is even: 7, 2, 2, 7, 5, 3, 3, 2, 2, 3, 5, 2, 7,...
%e 23 is in this sequence because A000120(3*23-1) = A000120(68) = 2 (even number).
%e 29 is in this sequence because A000120(3*29-1) = A000120(86) = 4 (even number).
%t Select[Prime@Range@200, EvenQ@ First@ DigitCount[3#-1, 2] &] (* _Giovanni Resta_, Jan 26 2014 *)
%o (PARI) isok(p) = isprime(p) && !(hammingweight(3*p-1) % 2); \\ _Michel Marcus_, Jan 18 2014
%Y Cf. A019434 (odd primes p having Hamming weight 2), A027697 (primes p having odd Hamming weight), A027699 (primes p having an even Hamming weight).
%K nonn,base
%O 1,1
%A _Juri-Stepan Gerasimov_, Jan 17 2014
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