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Search: id:A093456
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| A093456 |
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Product of composite numbers among next n numbers. |
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+0
3
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| 1, 1, 24, 720, 2520, 120960, 259459200, 1357171200, 4929724800, 42608389824000, 11912739135897600, 59907396092544000, 20458385028297216000, 7926428532945162240000, 4693751193479184764928000, 328774885640356760904499200000, 12797917159224592605450240000
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Conjecture: There are finitely many numbers such that a(n)is not == 0 (mod a(n-1). ( Also mentioned in A093455).
Product of all composite numbers between n*(n-1)/2+1 and n*(n+1)/2 (including boundaries). - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 02 2006
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EXAMPLE
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a(5) = 12*14*15 = 2520.
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MATHEMATICA
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Table[a := Range[n*(n - 1)/2 + 1, n*(n + 1)/2]; b := Select[a, Not[PrimeQ[ # ]] &]; Product[b[[i]], {i, 1, Length[b]}], {n, 1, 20}] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 02 2006
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CROSSREFS
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Cf. A093455.
Sequence in context: A006201 A118051 A160038 this_sequence A105187 A062313 A062528
Adjacent sequences: A093453 A093454 A093455 this_sequence A093457 A093458 A093459
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KEYWORD
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nonn,less
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 03 2004
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EXTENSIONS
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More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 02 2006
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