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 A085448 Primes having a semiprime number of 1's in their binary representation. 3

%I

%S 23,29,43,53,71,83,89,101,113,139,149,163,197,263,269,277,281,293,311,

%T 317,337,347,349,353,359,373,389,401,449,461,467,523,547,571,593,599,

%U 619,643,673,683,691,739,773,797,811,821,839,853,857,881,907,937,977

%N Primes having a semiprime number of 1's in their binary representation.

%C Sequence of least prime with the number of 1's in its binary representation equal to n-th semiprime is: 23,311,991,2039,73727,63487,4128767,... What is the prime corresponding to 22?

%H Amiram Eldar, <a href="/A085448/b085448.txt">Table of n, a(n) for n = 1..10000</a>

%e The prime 43 = '101011' has four 1's and so is a term.

%t seqQ[n_] := PrimeQ[n] && PrimeOmega[DigitCount[n, 2, 1]] == 2; Select[Range[1000], seqQ] (* _Amiram Eldar_, Dec 14 2019 *)

%Y Cf. A001358, A081092.

%K easy,nonn,base

%O 1,1

%A _Jason Earls_, Aug 14 2003

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Last modified September 24 12:34 EDT 2021. Contains 347642 sequences. (Running on oeis4.)