%I #18 Feb 04 2021 11:23:54
%S 8,12,18,27,30,45,50,63,70,75,80,98,105,112,125,128,147,154,165,168,
%T 175,176,182,192,195,208,220,231,242,245,260,264,273,275,286,312,325,
%U 338,340,343,357,363,374,380,385,396,399,408
%N Badly sieved numbers (A066680) which are not primes.
%H Reinhard Zumkeller, <a href="/A066681/b066681.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/Si#sieve">Index entries for sequences generated by sieves</a>
%F A099104(a(n))*A005171(a(n)) = 1. [_Reinhard Zumkeller_, Nov 12 2009]
%e 8 is the first nonprime in A066680, as multiples of 2 are marked only up to 4 = 2^2 and all other multiples of unmarked numbers < 8 do not hit 8.
%o (Haskell)
%o a066681 n = a066681_list !! (n-1)
%o a066681_list = filter ((== 0) . a010051) a066680_list
%o -- _Reinhard Zumkeller_, Feb 17 2012
%Y Cf. A010051.
%K nonn
%O 1,1
%A _Reinhard Zumkeller_, Dec 31 2001