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Search: id:A054988
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| A054988 |
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Number of prime divisors of 1 + (product of first n primes). |
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+0
8
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| 1, 1, 1, 1, 1, 2, 3, 2, 2, 3, 1, 3, 3, 2, 3, 4, 4, 2, 2, 4, 2, 3, 2, 4, 3, 2, 4, 4, 3, 3, 5, 3, 6, 2, 3, 2, 5, 4, 4, 2, 6, 3, 4
(list; graph; listen)
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OFFSET
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1,6
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LINKS
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Hisanori Mishima, Factorizations of many number sequences
R. G. Wilson v, Explicit factorizations
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EXAMPLE
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a(6)=2 because 2*3*5*7*11*13+1 = 30031 = 59 * 509
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MATHEMATICA
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a[q_] := Module[{x, n}, x=FactorInteger[Product[Table[Prime[i], {i, q}][[j]], {j, q}]+1]; n=Length[x]; Sum[Table[x[[i]][[2]], {i, n}][[j]], {j, n}]]
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CROSSREFS
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Cf. A000040 (prime numbers), A001359 (twin primes). Also A054989, A054990, A054991, A054992.
Sequence in context: A145390 A128049 A104543 this_sequence A143393 A166497 A116909
Adjacent sequences: A054985 A054986 A054987 this_sequence A054989 A054990 A054991
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KEYWORD
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nonn,hard
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AUTHOR
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Arne Ring (arne.ring(AT)epost.de), May 30 2000
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 24 2001
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