A071596 - OEIS

%I #12 Jan 11 2020 06:40:48

%S 2,4,6,8,10,12,16,18,20,24,32,34,36,40,42,48,64,68,70,72,80,84,96,128,

%T 136,138,140,144,160,168,192,210,256,266,272,276,280,288,290,320,322,

%U 330,336,384,390,420,512,514,518,522,530,532,544,552,560,576,580,640

%N 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.

%H Amiram Eldar, <a href="/A071596/b071596.txt">Table of n, a(n) for n = 1..10000</a>

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

%t Select[Range[2, 640, 2], DigitCount[#, 2, 1] == PrimeNu[#] &] (* _Amiram Eldar_, Jan 11 2020 *)

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

%Y Cf. A071594, A071595.

%K base,easy,nonn

%O 1,1

%A _Benoit Cloitre_, Jun 01 2002