A200246 - OEIS

%I #20 Jul 02 2024 22:31:38

%S 1,0,0,1,1,1,0,1,0,0,1,1,1,0,1,0,1,1,1,0,1,1,0,0,1,0,1,1,1,0,1,1,1,0,

%T 0,1,1,0,1,1,1,1,1,1,0,1,1,1,1,1,1,1,1,1,0,0,0,1,0,0,1,0,1,0,1,0,1,0,

%U 0,0,0,0,1,0,1,0,0,1,0,1,1,1,1,1,1,1

%N a(n)=1 iff binary weight of n-th prime is odd.

%C Characteristic function of A027698.

%H T. D. Noe, <a href="/A200246/b200246.txt">Table of n, a(n) for n = 1..1000</a>

%t If[OddQ[Total[IntegerDigits[#,2]]],1,0]&/@Prime[Range[90]] (* _Harvey P. Dale_, Jun 04 2012 *)

%o (Magma) [IsOdd(&+Intseq(NthPrime(n),2)) select 1 else 0: n in [1..100]]; // _Bruno Berselli_, Nov 16 2011

%o (PARI) a(n) = hammingweight(prime(n))%2; \\ _Ruud H.G. van Tol_, Jul 02 2024

%Y Cf. A010060, A027698, A200244.

%K nonn

%O 1

%A _N. J. A. Sloane_, Nov 15 2011