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Primes whose binary complement (A035327) is a square.
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%I #13 Jan 10 2019 16:20:57

%S 2,3,7,11,31,47,59,127,191,239,251,367,827,1019,1471,1723,2011,2939,

%T 4079,4091,4591,6427,7867,8191,10607,11483,12539,13679,13883,14447,

%U 14783,14939,15227,15359,16127,16187,16319,18367,26683,27583,28411,29167,29851,32191

%N Primes whose binary complement (A035327) is a square.

%t Select[Prime@ Range[10^4], IntegerQ@ Sqrt@ FromDigits[IntegerDigits[#, 2] /. {0 -> 1, 1 -> 0}, 2] &] (* _Michael De Vlieger_, Jan 04 2019 *)

%o (PARI) bc(n) = bitxor(n, 2^(1+logint(max(n, 1), 2))-1); \\ A035327

%o isok(n) = isprime(n) && issquare(bc(n)); \\ _Michel Marcus_, Jan 04 2019

%Y Cf. A000040, A035327, A000290, A323066.

%K nonn,base

%O 1,1

%A _Alex Ratushnyak_, Jan 03 2019