A125174 -id:A125174 - cp's OEIS frontend

Showing 1-1 of 1 results.

A087146 Numbers k such that k! + (k+1)! - 1 is prime.

Original entry on oeis.org

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

Offset: 1

Farideh Firoozbakht, Aug 19 2003

nonn

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

			3 is in the sequence because 3!+4!-1=29 is prime.

H. Dubner, Factorial and primorial primes, J. Rec. Math., 19(No. 3, 1987)

Cf. A087147, A051856, A125174 (corresponding primes).

v={}; Do[If[PrimeQ[n!+(n+1)!-1], v=Append[v, n]; Print[v]], {n, 1800}]; v

One more term from Ryan Propper, Aug 13 2005

a(21)-a(26) from Robert Price, Jul 12 2015

Showing 1-1 of 1 results.