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Search: id:A064237
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| A064237 |
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Numbers n such that n! + 1 is divisible by a square. |
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+0
4
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OFFSET
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1,1
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COMMENT
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229 is another term because 613^2 divides 229!+1. See A117186 for primes whose square divides m!+1 for some m. An examination of the factorizations of m!+1 for m<=100 found no additional squares. - T. D. Noe (noe(AT)sspectra.com), Mar 01 2006
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LINKS
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Hisanori Mishima, Factorizations of m!+1
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EXAMPLE
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23 is a term because 23!+1 =47^2*79*148139754736864591.
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MATHEMATICA
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SemiPrimeQ[n_] := (n>1) && (2==Plus@@(Transpose[FactorInteger[n]][[2]])); Select[Prime[Range[150]], SemiPrimeQ[ #+2] && !IntegerQ[Sqrt[ #+2]]&] Flatten[Position[MoebiusMu[Range[30]!+1], 0]]. - T. D. Noe (noe(AT)sspectra.com), Mar 01 2006
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CROSSREFS
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Sequence in context: A112918 A138920 A048224 this_sequence A139373 A069575 A072215
Adjacent sequences: A064234 A064235 A064236 this_sequence A064238 A064239 A064240
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KEYWORD
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nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Sep 22 2001
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EXTENSIONS
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562 is also a term because 562!+1 is divisible by 563^2. - Vladeta Jovovic (vladeta(AT)Eunet.yu), Mar 30 2004
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