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Search: id:A092967
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| A092967 |
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Largest prime of the form a squarefree number + 1 where the prime divisors of the squarefree number are < n. |
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+0
2
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| 2, 3, 7, 7, 31, 31, 211, 211, 211, 211, 2311, 2311, 6007, 6007, 6007, 6007, 102103, 102103, 3233231, 3233231, 3233231, 3233231, 17160991
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Conjecture: a(n)-1 has prime(n) -1 divisors. Subsidiary sequence: Number of primes of the from 2*p*q*r*...+ 1 where p,q,r etc. are distinct odd primes < n.
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EXAMPLE
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a(13) =6007= 2*3*7*11*13 + 1, as 2*5*7*11*13+ 1 etc. are composite.
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MATHEMATICA
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<<DiscreteMath`; <<NumberTheory`; Do[l = Select[Map[Times @@ #&, Subsets[Range[n]]], SquareFreeQ]; Print[Max[Select[Map[ #+1&, l], PrimeQ]]], {n, 1, 30}] (Propper)
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CROSSREFS
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Cf. A092965, A060957.
Sequence in context: A027672 A104138 A083809 this_sequence A056431 A011027 A100072
Adjacent sequences: A092964 A092965 A092966 this_sequence A092968 A092969 A092970
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 26 2004
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EXTENSIONS
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More terms from Ryan Propper (rpropper(AT)stanford.edu), Aug 13 2005
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