cp's OEIS Frontend

A320630 Products of primes of nonprime squarefree index.

%I A320630 #5 Oct 18 2018 08:50:23
%S A320630 2,4,8,13,16,26,29,32,43,47,52,58,64,73,79,86,94,101,104,113,116,128,
%T A320630 137,139,146,149,158,163,167,169,172,181,188,199,202,208,226,232,233,
%U A320630 256,257,269,271,274,278,292,293,298,313,316,317,326,334,338,344,347
%N A320630 Products of primes of nonprime squarefree index.
%C A320630 The index of a prime number n is the number m such that n is the m-th prime.
%e A320630 The sequence of terms begins:
%e A320630     2 = prime(1)
%e A320630     4 = prime(1)^2
%e A320630     8 = prime(1)^3
%e A320630    13 = prime(6)
%e A320630    16 = prime(1)^4
%e A320630    26 = prime(1)*prime(6)
%e A320630    29 = prime(10)
%e A320630    32 = prime(1)^5
%e A320630    43 = prime(14)
%e A320630    47 = prime(15)
%e A320630    52 = prime(1)^2*prime(6)
%e A320630    58 = prime(1)*prime(10)
%e A320630    64 = prime(1)^6
%e A320630    73 = prime(21)
%e A320630    79 = prime(22)
%e A320630    86 = prime(1)*prime(14)
%e A320630    94 = prime(1)*prime(15)
%e A320630   101 = prime(26)
%e A320630   104 = prime(1)^3*prime(6)
%e A320630   113 = prime(30)
%e A320630   116 = prime(1)^2*prime(10)
%e A320630   128 = prime(1)^7
%t A320630 Select[Range[100],With[{f=PrimePi/@First/@FactorInteger[#]},And[And@@SquareFreeQ/@f,And@@Not/@PrimeQ/@f]]&]
%Y A320630 Cf. A000040, A006450, A007821, A018252, A056239, A076610, A112798, A302242, A302478, A320628, A320629, A320631, A320633.
%K A320630 nonn
%O A320630 1,1
%A A320630 _Gus Wiseman_, Oct 18 2018