A320630 Products of primes of nonprime squarefree index.

2, 4, 8, 13, 16, 26, 29, 32, 43, 47, 52, 58, 64, 73, 79, 86, 94, 101, 104, 113, 116, 128, 137, 139, 146, 149, 158, 163, 167, 169, 172, 181, 188, 199, 202, 208, 226, 232, 233, 256, 257, 269, 271, 274, 278, 292, 293, 298, 313, 316, 317, 326, 334, 338, 344, 347

Offset: 1

Author

Gus Wiseman, Oct 18 2018

Keywords

• nonn

Comments

The index of a prime number n is the number m such that n is the m-th prime.

Examples

			The sequence of terms begins:
    2 = prime(1)
    4 = prime(1)^2
    8 = prime(1)^3
   13 = prime(6)
   16 = prime(1)^4
   26 = prime(1)*prime(6)
   29 = prime(10)
   32 = prime(1)^5
   43 = prime(14)
   47 = prime(15)
   52 = prime(1)^2*prime(6)
   58 = prime(1)*prime(10)
   64 = prime(1)^6
   73 = prime(21)
   79 = prime(22)
   86 = prime(1)*prime(14)
   94 = prime(1)*prime(15)
  101 = prime(26)
  104 = prime(1)^3*prime(6)
  113 = prime(30)
  116 = prime(1)^2*prime(10)
  128 = prime(1)^7
		

Crossrefs

Cf. A000040, A006450, A007821, A018252, A056239, A076610, A112798, A302242, A302478, A320628, A320629, A320631, A320633.

Programs

Mathematica

Select[Range[100],With[{f=PrimePi/@First/@FactorInteger[#]},And[And@@SquareFreeQ/@f,And@@Not/@PrimeQ/@f]]&]