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Search: id:A087400
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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
1
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| 13, 163, 2803, 3565153, 210344143, 86915972211813115391953, 4419764102942908730796303703, 114681479899746991802547357477494803
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Piptorial numbers are the partial products of prime index primes. Sum of reciprocals = 0.08341509210884323904648676616..
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FORMULA
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Pips 3*5*11*17 = 2805 = p+2. p=2803.
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PROGRAM
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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.
Adjacent sequences: A087397 A087398 A087399 this_sequence A087401 A087402 A087403
Sequence in context: A118673 A133180 A090134 this_sequence A012828 A119539 A078362
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KEYWORD
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easy,nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Oct 21 2003
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