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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, 3901, 3981, 4682, 6569, 20266, 20662
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OFFSET
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1,2
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COMMENTS
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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.
a(1)-a(26) give certified primes. - Robert Price, Jul 12 2015
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REFERENCES
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H. Dubner, Factorial and primorial primes, J. Rec. Math., 19(No. 3, 1987)
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LINKS
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EXAMPLE
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3 is in the sequence because 3!+4!-1=29 is prime.
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MATHEMATICA
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v={}; Do[If[PrimeQ[n!+(n+1)!-1], v=Append[v, n]; Print[v]], {n, 1800}]; v
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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