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 A280999 #21 May 01 2021 07:32:44 %S A280999 7,8,12,14,15,16,17,19,23,24,25,27,28,29,30,33,34,35,36,38,39,40,44, %T A280999 46,47,49,50,51,52,54,55,57,58,59,61,63,64,66,68,69,70,72,73,75,76,77, %U A280999 78,80,81,83,87,88,89,91,92,93,94,96,98,100,101,102,104,105,107 %N A280999 Numbers with a prime number of 0's in their binary reflected Gray code representation. %H A280999 Indranil Ghosh, <a href="/A280999/b280999.txt">Table of n, a(n) for n = 1..10000</a> %H A280999 Wikipedia, <a href="https://en.wikipedia.org/wiki/Gray_code">Gray code</a>. %e A280999 27 is in the sequence because the binary reflected Gray Code representation of 27 is 10110 which has 2 0's and 2 is prime. %t A280999 Select[Range[100], PrimeQ[DigitCount[BitXor[#, Floor[#/2]], 2, 0]] &] (* _Amiram Eldar_, May 01 2021 *) %o A280999 (PARI) is(n)=isprime(logint(n,2)-hammingweight(bitxor(n, n>>1))+1) \\ _Charles R Greathouse IV_, Jan 13 2017 %Y A280999 Cf. A014550, A144754, A280998. %K A280999 nonn,base,easy %O A280999 1,1 %A A280999 _Indranil Ghosh_, Jan 12 2017