A233011 Primes of the form (2*n)! - n!^2 - 1.

19, 683, 478483199, 20921164185599

Offset

1,1

Comments

The 5th term a(5) has 268 digits and is too long to display in data section.

The 7th term a(7) in the sequence has 823 digits.

a(8) has 2030 digits; a(9) has 2264 digits (these are not included in b-file).

Links

K. D. Bajpai, Table of n, a(n) for n = 1..7

Example

a(1)= 19: n= 2: (2*n)!- n!^2-1= 19 which is prime.
a(2)= 683: n= 3: (2*n)!- n!^2-1= 683 which is prime.

Maple

KD := proc() local a; a:=(2*n)!-n!^2-1; if isprime(a) then RETURN (a);  fi; end: seq(KD(), n=1..200);

Crossrefs

Cf. A055490 (primes: n! -1).

Cf. A118812 (primes: (2*n)!-n!+1).

Sequence in context: A217825 A200849 A162012 * A369373 A280112 A231160

Adjacent sequences: A233008 A233009 A233010 * A233012 A233013 A233014

Keyword

nonn

Author

K. D. Bajpai, Dec 03 2013

Status

approved