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Search: id:A102926
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| A102926 |
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Smallest prime factor in product of previous terms +1 or -1. |
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+0
2
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| 2, 3, 5, 29, 11, 7, 13, 37, 17, 79, 23, 4129, 193, 2593, 101, 19, 39163, 577, 26431, 131, 308798542881428667318174028327605372989, 103, 163, 179, 293, 127, 6287, 683437, 31, 89, 13590243019242466336587034391, 113, 2207, 59, 109, 223, 2351
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A variant of the Euclid-Mullin construction.
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LINKS
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Donovan Johnson, Table of n, a(n) for n = 1..111
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FORMULA
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a(n) = least prime factor of b(n)^2-1, where b(n) = product a(k), 0<k<n, = A102927.
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EXAMPLE
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a(5)=11 because 2*3*5*29=870, 869=11*79, 871=13*67.
a(31) = 13590243019242466336587034391 because this is the least prime factor of A102927(30)+1. The least prime factor of A102927(30)-1 is 44989026625856465412069667987. Remarkably, both are 29-digit numbers. - David Wasserman (dwasserm(AT)earthlink.net), Apr 15 2008
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CROSSREFS
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Cf. A000945, A000946, A005265, A102927.
Sequence in context: A042669 A041585 A042935 this_sequence A084598 A038962 A019400
Adjacent sequences: A102923 A102924 A102925 this_sequence A102927 A102928 A102929
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KEYWORD
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nonn
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AUTHOR
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Marc LeBrun (mlb(AT)well.com), Jan 19 2005
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EXTENSIONS
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More terms from Don Reble (djr(AT)nk.ca), Jan 23 2005, corrected Sep 26 2006
Further terms from David Wasserman (dwasserm(AT)earthlink.net), Apr 15 2008
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