This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A235985 #21 Jan 27 2014 18:25:42 %S A235985 2,7,23,29,31,71,103,107,109,113,127,151,157,167,199,227,229,233,263, %T A235985 283,313,347,349,359,367,373,379,383,431,433,439,443,449,457,461,463, %U A235985 467,479,487,491,499,503,509,541,569,599,607,619,631,647,739,761,797 %N A235985 Primes p such that 3p-1 has even Hamming weight. %C A235985 Primes p such that A000120(3p-1) is even. %C A235985 Smallest prime p such that A000120(np-1) is even: 7, 2, 2, 7, 5, 3, 3, 2, 2, 3, 5, 2, 7,... %e A235985 23 is in this sequence because A000120(3*23-1) = A000120(68) = 2 (even number). %e A235985 29 is in this sequence because A000120(3*29-1) = A000120(86) = 4 (even number). %t A235985 Select[Prime@Range@200, EvenQ@ First@ DigitCount[3#-1, 2] &] (* _Giovanni Resta_, Jan 26 2014 *) %o A235985 (PARI) isok(p) = isprime(p) && !(hammingweight(3*p-1) % 2); \\ _Michel Marcus_, Jan 18 2014 %Y A235985 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 A235985 nonn,base %O A235985 1,1 %A A235985 _Juri-Stepan Gerasimov_, Jan 17 2014