A071596 Even numbers k such that the number of 1's in binary representation of k equals omega(k), the number of distinct primes in the factorization of k.

2, 4, 6, 8, 10, 12, 16, 18, 20, 24, 32, 34, 36, 40, 42, 48, 64, 68, 70, 72, 80, 84, 96, 128, 136, 138, 140, 144, 160, 168, 192, 210, 256, 266, 272, 276, 280, 288, 290, 320, 322, 330, 336, 384, 390, 420, 512, 514, 518, 522, 530, 532, 544, 552, 560, 576, 580, 640

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

532 = 1000010100 in base 2 and 532 = 2^2*7*19 hence 532 is in the sequence.

Mathematica

Select[Range[2, 640, 2], DigitCount[#, 2, 1] == PrimeNu[#] &] (* Amiram Eldar, Jan 11 2020 *)

Prog

(PARI) for(n=1, 80000, if(sum(i=1, length(binary(n)), component(binary(n), i))==(-1)^n*omega(n), print1(n, ", ")))

Crossrefs

Cf. A071594, A071595.

Sequence in context: A177917 A071594 A306263 * A090778 A097380 A114270

Adjacent sequences: A071593 A071594 A071595 * A071597 A071598 A071599

Keyword

base,easy,nonn

Author

Benoit Cloitre, Jun 01 2002

Status

approved