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A320628 Products of primes of nonprime index. 6
1, 2, 4, 7, 8, 13, 14, 16, 19, 23, 26, 28, 29, 32, 37, 38, 43, 46, 47, 49, 52, 53, 56, 58, 61, 64, 71, 73, 74, 76, 79, 86, 89, 91, 92, 94, 97, 98, 101, 103, 104, 106, 107, 112, 113, 116, 122, 128, 131, 133, 137, 139, 142, 146, 148, 149, 151, 152, 158, 161, 163 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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..61.

EXAMPLE

The sequence of terms begins:

   1 = 1

   2 = prime(1)

   4 = prime(1)^2

   7 = prime(4)

   8 = prime(1)^3

  13 = prime(6)

  14 = prime(1)*prime(4)

  16 = prime(1)^4

  19 = prime(8)

  23 = prime(9)

  26 = prime(1)*prime(6)

  28 = prime(1)^2*prime(4)

  29 = prime(10)

  32 = prime(1)^5

  37 = prime(12)

  38 = prime(1)*prime(8)

  43 = prime(14)

  46 = prime(1)*prime(9)

  47 = prime(15)

  49 = prime(4)^2

  52 = prime(1)^2*prime(6)

  53 = prime(16)

  56 = prime(1)^3*prime(4)

  58 = prime(1)*prime(10)

  61 = prime(18)

  64 = prime(1)^6

  71 = prime(20)

  73 = prime(21)

  74 = prime(1)*prime(12)

  76 = prime(1)^2*prime(8)

  79 = prime(22)

  86 = prime(1)*prime(14)

  89 = prime(24)

  91 = prime(4)*prime(6)

  92 = prime(1)^2*prime(9)

  94 = prime(1)*prime(15)

  97 = prime(25)

  98 = prime(1)*prime(4)^2

MATHEMATICA

Select[Range[100], And@@Not/@PrimeQ/@PrimePi/@First/@FactorInteger[#]&]

CROSSREFS

Cf. A006450, A007821, A018252, A056239, A076610, A290103, A302242, A302478, A320533, A320629, A320630, A320631, A320633.

Sequence in context: A215822 A079374 A236217 * A260488 A190808 A018614

Adjacent sequences:  A320625 A320626 A320627 * A320629 A320630 A320631

KEYWORD

nonn

AUTHOR

Gus Wiseman, Oct 18 2018

STATUS

approved

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Last modified October 18 23:39 EDT 2019. Contains 328211 sequences. (Running on oeis4.)