A118744 Primes of the form n!! + n - 1.

3, 5, 11, 19, 53, 953, 46091, 34459441, 3715891219, 6332659870762850657, 107145471557284795514880041

Offset

1,1

Comments

No additional terms up to n=2000. - Harvey P. Dale, Jul 27 2017

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..11.

Example

For n=2, 2!! + 2 - 1 = 2 + 2 - 1 = 3, which is prime;
for n=4, 4!! + 4 - 1 = 4*2 + 4 - 1 = 11, 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(i+k-1) then print(i+k-1); fi; od: end: SFACT(550);

Mathematica

Select[Table[n!!+n-1, {n, 100}], PrimeQ] (* Harvey P. Dale, Jul 27 2017 *)

Crossrefs

Sequence in context: A117272 A243616 A147189 * A092672 A061068 A263925

Adjacent sequences: A118741 A118742 A118743 * A118745 A118746 A118747

Keyword

nonn

Author

Paolo P. Lava and Giorgio Balzarotti, May 22 2006

Status

approved