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Search: id:A081617
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| A081617 |
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Smallest k such that (product of first n primes)*k+1 is divisible by the (n+1)-th prime. Also (A075306(n)-1)/A002110(n). |
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+0
2
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| 1, 4, 3, 10, 10, 2, 1, 3, 17, 13, 10, 34, 38, 4, 51, 55, 51, 29, 68, 13, 59, 30, 27, 45, 18, 92, 77, 82, 64, 14, 68, 58, 114, 68, 8, 77, 42, 114, 31, 98, 129, 110, 43, 61, 159, 35, 109, 60, 91, 149, 193, 2, 38, 120, 259, 147, 135, 22, 140, 10, 263, 285, 286, 134, 308
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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The 8th prime, 19, divides 2*3*5*7*11*13*17+1=510511, thus a(7)=1.
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PROGRAM
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(PARI) for(n=1, 100, p=1:forprime(k=2, prime(n), p=p*k):pn=prime(n+1):s=0:while((s+1)%pn>0, s=s+p):print1(s/p", "))
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CROSSREFS
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Cf. A081618 (positions of unity).
Adjacent sequences: A081614 A081615 A081616 this_sequence A081618 A081619 A081620
Sequence in context: A107381 A132192 A075563 this_sequence A103252 A065763 A100492
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KEYWORD
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nonn
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AUTHOR
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Ralf Stephan (ralf(AT)ark.in-berlin.de), Mar 24 2003
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