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A135715
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Number of primes of the form p(n)#/p(k) + 1, where 1 <= k <= n.
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3
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1, 1, 2, 3, 3, 3, 3, 2, 2, 3, 4, 5, 2, 1, 3, 2, 3, 1, 0, 1, 1, 4, 5, 0, 0, 2, 1, 1, 3, 2, 1, 3, 0, 3, 1, 1, 2, 2, 6, 2, 4, 1, 4, 4, 3, 4, 3, 2, 4, 1, 0, 3, 3, 3, 4, 2, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 2, 3, 3, 1, 3, 2, 2, 2, 4, 4, 2, 2, 0, 1, 3, 1, 1, 3, 1, 1, 0, 1, 0, 4, 1, 1, 4, 1, 1, 1, 2, 4, 1, 1, 2, 2, 3, 7, 3
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| p(k) is k-th prime; p(n)# is n-th primorial, A002110(n). For the larger n, these are only counts of highly probable primes. Of the first 500 terms, the maximum occurs once, a(172)=8; the mode is 2, occurring 135 times.
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LINKS
| Rick L. Shepherd, Table of n, a(n) for n = 1..500
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EXAMPLE
| a(3)=2 because p(3)#=A002110(3)=30 and 30/3+1=11 and 30/5+1=7 are both prime and there are no other primes of this form.
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PROG
| (PARI) a(n)= p=prod(k=1, n, prime(k)); sum(k=1, n, isprime(p/prime(k)+1))
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CROSSREFS
| Cf. A135714, A135716, A002110.
Sequence in context: A127661 A008968 A162499 * A089326 A022923 A192454
Adjacent sequences: A135712 A135713 A135714 * A135716 A135717 A135718
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KEYWORD
| nonn
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AUTHOR
| Rick L. Shepherd (rshepherd2(AT)hotmail.com), Nov 30 2007
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