OFFSET
1,4
COMMENTS
Indices of 1's: A002981.
MATHEMATICA
Table[k = 1; While[! PrimeQ[k!*n! + 1], k++]; k, {n, 100}] (* T. D. Noe, Nov 18 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Nov 15 2013
STATUS
approved