A161186 In the sequence of nonprime numbers, an element k's position is either prime or nonprime. If k's position is prime, a(k)= the k-th nonprime-positioned element, else a(k) is the k-th prime-positioned element. Iterated application gives disjoint sequences generated by the first elements, which form the sequence above. {a(1)} = {1,4,14,60,...}, {a(6)} = {6,16,74,...}, {a(8)} ={8,28,56,...}. The generators are the first elements, {1,6,8,...etc}.

1, 6, 8, 9, 10, 12, 15, 18