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A057017
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Product of first n composite numbers minus 1 is a prime.
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1
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1, 2, 3, 9, 12, 22, 26, 30, 34, 51, 54, 100, 125, 155, 168, 173, 220, 401, 494
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| a(3) = 3 because 4*6*8-1 = 191 which is prime.
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MATHEMATICA
| Composite[ n_Integer ] := (k = n + PrimePi[ n ] + 1; While[ k - PrimePi[ k ] - 1 != n, k++ ]; k); Do[ m = n; If[ PrimeQ[ Product[ Composite[ k ], {k, 1, n} ] - 1 ], Print[ n ] ], {n, 1, 1980} ]
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CROSSREFS
| Cf. A053982.
Sequence in context: A168080 A048084 A067719 * A047162 A155929 A175206
Adjacent sequences: A057014 A057015 A057016 * A057018 A057019 A057020
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 21 2001
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