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

1,1

Comments

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

Links

Table of n, a(n) for n=1..56.

Example

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

Mathematica

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

Crossrefs

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

Sequence in context: A076202 A268713 A363594 * A224399 A114398 A107326

Adjacent sequences: A320627 A320628 A320629 * A320631 A320632 A320633

Keyword

nonn

Author

Gus Wiseman, Oct 18 2018

Status

approved