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A087400
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Primes p such that p+2 is a piptorial number. Also numbers such that A080696(n)- 2 is prime.
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0
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OFFSET
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1,1
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COMMENTS
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Piptorial numbers are the partial products of prime-indexed primes. Sum of reciprocals = 0.08341509210884323904648676616...
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LINKS
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Table of n, a(n) for n=1..8.
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FORMULA
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(Product of first four pips) - 2 = 3*5*11*17 - 2 = 2805 - 2 = 2803, which is prime, so 2803 is in the sequence.
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PROG
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(PARI) piptorial(n) = { s=0; p=1; for(x=1, n, p=p*prime(prime(x)); if(isprime(p-2), print1(p-2", "); s+=1.0/(p-2)) ); print(); print(s) }
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CROSSREFS
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Cf. A080696.
Sequence in context: A212785 A133180 A090134 * A012828 A119539 A277412
Adjacent sequences: A087397 A087398 A087399 * A087401 A087402 A087403
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard, Oct 21 2003
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STATUS
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approved
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