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A320630 Products of primes of nonprime squarefree index. 3
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 (list; graph; refs; listen; history; text; internal format)
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: A133802 A076202 A268713 * A224399 A114398 A107326

Adjacent sequences:  A320627 A320628 A320629 * A320631 A320632 A320633

KEYWORD

nonn

AUTHOR

Gus Wiseman, Oct 18 2018

STATUS

approved

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Last modified September 16 08:53 EDT 2019. Contains 327092 sequences. (Running on oeis4.)