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 A087146 Numbers n such that n!+(n+1)!-1 is prime. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 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. a(27) > 25000. - Robert Price, Jul 12 2015 a(1)-a(26) give certified primes. - Robert Price, Jul 12 2015 REFERENCES H. Dubner, Factorial and primorial primes, J. Rec. Math., 19(No. 3, 1987) LINKS EXAMPLE 3 is in the sequence because 3!+4!-1=29 is prime. MATHEMATICA v={}; Do[If[PrimeQ[n!+(n+1)!-1], v=Append[v, n]; Print[v]], {n, 1800}]; v CROSSREFS Cf. A087147, A051856. Sequence in context: A000861 A108168 A245905 * A033945 A098142 A270812 Adjacent sequences:  A087143 A087144 A087145 * A087147 A087148 A087149 KEYWORD nonn AUTHOR Farideh Firoozbakht, Aug 19 2003 EXTENSIONS One more term from Ryan Propper, Aug 13 2005 a(21)-a(26) from Robert Price, Jul 12 2015 STATUS approved

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Last modified March 19 13:25 EDT 2019. Contains 321330 sequences. (Running on oeis4.)