A237580 a(n) = (2n)! - n! + 1.

1, 2, 23, 715, 40297, 3628681, 479000881, 87178286161, 20922789847681, 6402373705365121, 2432902008173011201, 1124000727777567763201, 620448401733238960358401, 403291461126605629356979201, 304888344611713860414325708801, 265252859812191058635000805632001

Offset: 0

Author

M. F. Hasler, Feb 09 2014

Keywords

• nonn

Comments

Primes are listed in A118812, the corresponding indices in A237443; the least prime factor of a(n) in A237579.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..100

Crossrefs

Cf. A000142 (n!), A010050 ((2n)!)

Programs

Magma

[Factorial(2*n)-Factorial(n)+1: n in [0..15]]; // Vincenzo Librandi, Feb 11 2014

Mathematica

Table[((2 n)! - n! + 1), {n, 0, 30}] (* Vincenzo Librandi, Feb 11 2014 *)

PARI

A237580 = n->(2*n)!-n!+1