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 A137331 #8 Mar 02 2015 02:13:16
%S A137331 0,0,0,1,0,1,1,1,0,1,1,1,1,1,1,0,0,1,1,1,1,1,1,0,1,1,1,0,1,0,0,1,0,1,
%T A137331 1,1,1,1,1,0,1,1,1,0,1,0,0,1,1,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,0,1,1,1,
%U A137331 1,1,1,0,1,1,1,0,1,0,0,1,1,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,1,1,0,1,0,0,1,1
%N A137331 a(n) = 1 if the binary weight of n is prime, otherwise 0.
%F A137331 a(n) = A010051(A000120(n)). - _R. J. Mathar_, Apr 09 2008
%e A137331 a(0) = 0 (binary). Bits set = 0, 0 not prime -> 0.
%e A137331 a(1) = 1 (binary). Bits set = 1, 1 not prime -> 0.
%e A137331 a(2) = 10 (binary). Bits set = 1, 1 not prime -> 0.
%e A137331 a(3) = 11 (binary). Bits set = 2, 2 prime -> 1.
%p A137331 A000120 := proc(n) add(i,i=convert(n,base,2)) ; end: A010051 := proc(n) if isprime(n) then 1 ; else 0 ; fi ; end: A137331 := proc(n) A010051(A000120(n)) ; end: seq(A137331(n),n=0..200) ; # _R. J. Mathar_, Apr 09 2008
%t A137331 Table[If[PrimeQ[Plus @@ IntegerDigits[n, 2]], 1, 0], {n, 0, 100}] (* _Stefan Steinerberger_, Apr 09 2008 *)
%o A137331 (PARI)f(n)={v=binary(n);s=0;for(k=1,#v,if(v[k]== 1,s++));return(isprime(s))};for(n=0,104,if(f(n),print1("1, "),print1("0, "))) \\ _Washington Bomfim_, Jan 14 2011
%Y A137331 Begins the same as A135136, but differs starting at a(31).
%K A137331 nonn,easy,base
%O A137331 0,1
%A A137331 _George Pollard_, Apr 07 2008
%E A137331 More terms from _R. J. Mathar_ and _Stefan Steinerberger_, Apr 09 2008