OFFSET
1,1
COMMENTS
991*n^2+1 is a square for n=12055735790331359447442538767.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
for n=6, 991*n^2+1=35677; n=46, 991*n^2+1=2090957.
MATHEMATICA
Select[Range[0, 1000], PrimeQ[991#^2+1]&] (* Vincenzo Librandi, Sep 24 2012 *)
PROG
(Magma) [n: n in [0..900] | IsPrime(991*n^2+1)]; Vincenzo Librandi, Sep 24 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Jan 18 2009
STATUS
approved