A027703 - OEIS

%I #20 Aug 06 2024 02:00:58

%S 5,17,29,43,53,71,89,101,113,149,163,197,269,281,293,311,317,359,373,

%T 389,401,449,461,479,509,523,547,571,599,619,643,673,691,739,751,773,

%U 797,821,857,863,881,907,937,983,1013,1031,1049,1061,1103,1117,1151

%N Primes with even number of 1's in binary expansion such that next prime has odd number of 1's.

%H Vincenzo Librandi, <a href="/A027703/b027703.txt">Table of n, a(n) for n = 1..2500</a>

%F a(n) = prime(A027704(n)). - _Michel Marcus_, Mar 29 2018

%t c[ n_ ] := OddQ[ Count[ IntegerDigits[ n, 2 ], 1 ] ]; Map[ Prime, Select[ Range[ 300 ], Not[ c[ Prime[ # ] ] ]&&c[ Prime[ #+1 ] ]& ] ]

%t Prime[#]&/@SequencePosition[Table[If[EvenQ[DigitCount[n,2,1]],1,0],{n, Prime[ Range[200]]}],{1,0}][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Apr 03 2019 *)

%Y Cf. A027704.

%Y Cf. A027701, A027705, A027707.

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_.

%E More terms from _Erich Friedman_.

%E Offset changed by _Michel Marcus_, Mar 29 2018