%I #5 Oct 13 2023 06:48:21
%S 1,2,6,9,15,20,25,28,35,42,45,49,63,66,77,88,91,99,104,110,117,121,
%T 130,143,153,156,165,169,170,187,190,195,204,209,221,228,231,238,247,
%U 255,266,272,273,276,285,289,299,304,322,323,325,342,345,350,357,361,368
%N Primitive elements of A071562.
%C Members of A071562 which cannot be expressed as the product of two smaller elements of that sequence.
%C This definition is made to include 1; it would make about as much sense to exclude it.
%C This sequence includes all numbers of the form a*p, where p/2 < a <= p, for p prime. It also includes all p*q*r, where p, q, and r are odd primes, and p*q/2 < r < p*q. Similar but increasingly complex conditions can be made for products of more primes.
%e 4 is not in the sequence, because 4 = 2*2, and 2 is in A071562.
%K nonn
%O 1,2
%A _Franklin T. Adams-Watters_, Apr 07 2010