A119497 Primes of the form n! + n!! + 1.

3, 5, 769, 1405006117752879898543142713389983127221179514880001

Offset

1,1

References

G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008, p. 159.

Links

Table of n, a(n) for n=1..4.

Example

For n=2, 2! + 2!! + 1 = 2 + 2 + 1 = 5, which is prime.
For n=6, 6! + 6!! + 1 = 720 + 48 + 1 = 769, which is prime.

Maple

SFACT:= proc(n) local i, j, k; for k from 1 by 1 to n do i:=k; j:=k-2; while j >0 do i:=i*j; j:=j-2; od: if isprime(k!+i+1) then print(k!+i+1); fi; od: end: SFACT(300);

Prog

(PARI) dfac(n)=prod(k=0, n\2-1, n-k-k)
for(n=1, 42, if(ispseudoprime(t=n!+dfac(n)+1), print1(t", "))); v \\ Charles R Greathouse IV, Feb 17 2011

Crossrefs

Cf. A118769.

Sequence in context: A002427 A350036 A136134 * A298094 A012783 A062655

Adjacent sequences: A119494 A119495 A119496 * A119498 A119499 A119500

Keyword

nonn

Author

Paolo P. Lava and Giorgio Balzarotti, May 25 2006

Extensions

No more terms with fewer than a thousand digits. - Charles R Greathouse IV, Feb 17 2011

Status

approved