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A087146
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Numbers n such that n!+(n+1)!-1 is prime.
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1
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1, 2, 3, 5, 9, 13, 14, 17, 27, 28, 33, 39, 103, 115, 205, 291, 1431, 1532, 1710, 1937
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| 291 is in the sequence and also is in the sequence A087147, thus (291!+292!-1,291!+292!+1) is a twin pair of primes. Any additional terms are greater than 1800 with the next prime having more than 5086 digits.
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REFERENCES
| H. Dubner, Factorial and primorial primes, J. Rec. Math., 19(No. 3, 1987)
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EXAMPLE
| 3 is in the sequence because 3!+4!-1=29 is prime.
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MATHEMATICA
| v={}; Do[If[PrimeQ[n!+(n+1)!-1], v=Append[v, n]; Print[v]], {n, 1800}]; v
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CROSSREFS
| Cf. A087147, A051856.
Sequence in context: A079741 A000861 A108168 * A033945 A098142 A066821
Adjacent sequences: A087143 A087144 A087145 * A087147 A087148 A087149
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KEYWORD
| nonn
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AUTHOR
| Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Aug 19 2003
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EXTENSIONS
| One more term from Ryan Propper (rpropper(AT)stanford.edu), Aug 13 2005
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