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

19, 683, 478483199, 20921164185599

Offset: 1

Author

K. D. Bajpai, Dec 03 2013

Keywords

• nonn

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).

Examples

			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.
		

Links

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

Crossrefs

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

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

Programs

Maple

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