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Numbers k such that the k-th prime has an odd number of 1's in its binary expansion.
4

%I #17 Sep 19 2021 17:51:35

%S 1,4,5,6,8,11,12,13,15,17,18,19,21,22,25,27,28,29,31,32,33,36,37,39,

%T 40,41,42,43,44,46,47,48,49,50,51,52,53,54,58,61,63,65,67,73,75,78,80,

%U 81,82,83,84,85,86,88,90,93,94,95,98,100,102,103,104,106,107,110,111,112

%N Numbers k such that the k-th prime has an odd number of 1's in its binary expansion.

%H T. D. Noe, <a href="/A027698/b027698.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[ Range[ 150 ], OddQ[ Length[ Cases[ IntegerDigits[ Prime[ # ], 2 ], 1 ] ] ]& ]

%t Select[Range[200],OddQ[DigitCount[Prime[#],2,1]]&] (* _Harvey P. Dale_, Sep 19 2021 *)

%Y Cf. A027697, A027699, A027700.

%K nonn,easy

%O 1,2

%A _N. J. A. Sloane_

%E More terms from _Erich Friedman_