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.
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
KEYWORD
nonn
AUTHOR
Paolo P. Lava and Giorgio Balzarotti, May 22 2006
STATUS
approved