A118743 Primes of the form n!! + n + 1.

3, 5, 7, 13, 113, 3851, 46093, 10321937, 185794579, 216862434431944426122117120047, 1874480713189654839282450157086195210900931486780353469173376681742503659434414632312033372643386765197475111737132341321962070865661132800000000000000000173

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..11.

Example

For n=2, 2!! + 2 + 1 = 2 + 2 + 1 = 5, which is prime;
for n=4, 4!! + 4 + 1 = 4*2 + 4 + 1 = 8 + 4 + 1 = 13, 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, 250}], PrimeQ] (* Harvey P. Dale, Nov 22 2012 *)

Crossrefs

Sequence in context: A236464 A064268 A235873 * A225226 A333630 A114980

Adjacent sequences: A118740 A118741 A118742 * A118744 A118745 A118746

Keyword

nonn

Author

Paolo P. Lava and Giorgio Balzarotti, May 22 2006

Status

approved