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A100959 Non-semiprimes.

%I A100959 #24 Feb 16 2025 08:32:55
%S A100959 1,2,3,5,7,8,11,12,13,16,17,18,19,20,23,24,27,28,29,30,31,32,36,37,40,
%T A100959 41,42,43,44,45,47,48,50,52,53,54,56,59,60,61,63,64,66,67,68,70,71,72,
%U A100959 73,75,76,78,79,80,81,83,84,88,89,90,92,96,97,98,99,100,101,102,103,104
%N A100959 Non-semiprimes.
%C A100959 A001222(a(n)) <> 2; a(n) <> A020639(a(n)) * A006530(a(n)); complement of A001358; A064911(a(n)) = 0.
%C A100959 A174956(a(n)) = 0. - _Reinhard Zumkeller_, Apr 03 2010
%H A100959 Donald Alan Morrison, <a href="/A100959/b100959.txt">Table of n, a(n) for n = 1..10000</a>
%H A100959 Donald Alan Morrison, <a href="/A100959/a100959.txt">Sage program</a>
%H A100959 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Semiprime.html">Semiprime</a>
%F A100959 a(n) = n + O(n log log n/log n). - _Charles R Greathouse IV_, Dec 29 2024
%t A100959 Select[Range[120], ! PrimeOmega[#] == 2 &] (* _Vincenzo Librandi_, Jun 14 2014 *)
%o A100959 (PARI) isok(n) = (bigomega(n) != 2) \\ _Michel Marcus_, Aug 01 2013
%o A100959 (Python)
%o A100959 from math import isqrt
%o A100959 from sympy import prime, primepi
%o A100959 def A100959(n):
%o A100959     def f(x): return n+int(sum(primepi(x//prime(k))-k+1 for k in range(1,primepi(isqrt(x))+1)))
%o A100959     m, k = n, f(n)
%o A100959     while m != k:
%o A100959         m, k = k, f(k)
%o A100959     return m # _Chai Wah Wu_, Jul 23 2024
%K A100959 nonn,easy
%O A100959 1,2
%A A100959 _Reinhard Zumkeller_, Nov 24 2004