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Positions of primes in A167171.
1

%I #11 May 15 2017 16:05:44

%S 1,2,3,5,7,8,11,12,15,17,18,22,25,26,28,30,34,35,38,40,41,44,46,50,55,

%T 56,57,59,60,62,68,70,73,74,80,81,83,87,89,90,93,94,98,99,101,102,109,

%U 117,119,120,121,124,125,128,131,134,137,138,140,142

%N Positions of primes in A167171.

%C Complement of A182800.

%e A167171=(2,3,5,6,7,10,11,13,14,15,17,19,21,22,23,...) consists of primes and products p*q of distinct primes.

%e a(1)=1 because 2 is in position 1;

%e a(4)=5 because 7 is in position 5.

%o (PARI) lista(nn) = {nb = 0; for (n=1, nn, if (numdiv(n) == 2*omega(n), nb++; if (isprime(n), print1(nb, ", "));););} \\ _Michel Marcus_, May 15 2017

%Y Cf. A000040, A167171, A182800.

%K nonn

%O 1,2

%A _Clark Kimberling_, Dec 03 2010