A027704 Numbers k such that the k-th prime has an even number of 1's in its binary expansion and the (k+1)st prime has an odd number of 1's.

3, 7, 10, 14, 16, 20, 24, 26, 30, 35, 38, 45, 57, 60, 62, 64, 66, 72, 74, 77, 79, 87, 89, 92, 97, 99, 101, 105, 109, 114, 117, 122, 125, 131, 133, 137, 139, 142, 148, 150, 152, 155, 159, 166, 170, 173, 176, 178, 185, 187, 190, 194, 201, 203, 206, 209, 211, 215, 223

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

Primes:= [seq(ithprime(i), i=1..100)]:
Q:= map(t -> convert(convert(t, base, 2), `+`) mod 2, Primes):
DQ:= Q[2..-1]-Q[1..-2]:
select(t -> DQ[t] = 1, [$1..nops(DQ)]); # Robert Israel, Mar 27 2018

Prog

(PARI) isok(n) = my(p=prime(n)); !(hammingweight(p) % 2) && (hammingweight(nextprime(p+1)) % 2); \\ Michel Marcus, Mar 29 2018

Crossrefs

Cf. A027703 (corresponding primes).

Cf. A027702, A027704, A027706.

Cf. A027701, A027703, A027705.

Sequence in context: A374639 A289114 A289027 * A061289 A288999 A310187

Adjacent sequences: A027701 A027702 A027703 * A027705 A027706 A027707

Keyword

nonn,easy,base

Author

N. J. A. Sloane

Extensions

More terms from Erich Friedman

Status

approved