OFFSET
1,1
COMMENTS
Primes of the form A010790(k)-1 or A010790(k)+1. This is the 3rd sequence in the supersequence whose first member is factorial primes, A002981 UNION A002982, and whose 2nd member is A176038 Primes of the form n!*(n+1)! - 1 or n!*(n+1)! + 1.
a(9) has already 486 digits and is not listed for that reason. The sequence is generated by the n-values 0, 1, 1, 4, 6, 9, 13, 19, 101, 196,... [From R. J. Mathar, Oct 03 2010]
a(9) also ends with 72 nines. - Harvey P. Dale, Jan 05 2013
EXAMPLE
a(2) = 11 because 1!*(1+1)!*(1+2)! - 1 = 11 is prime. a(4) = 2073601 because 4!*(4+1)!*(4+2)! + 1 = 2073601 is prime. a(7) because 13!*(13+1)!*(13+2)! - 1 = 709885457731229765106401279999999 is prime.
MATHEMATICA
Select[Union[Flatten[Times@@#+{1, -1}&/@Partition[Range[0, 30]!, 3, 1]]], PrimeQ] (* Harvey P. Dale, Jan 05 2013 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Apr 07 2010
EXTENSIONS
a(8) from R. J. Mathar, Oct 03 2010
STATUS
approved