OFFSET
1,1
COMMENTS
Or numbers n such that the smallest prime divisor of n^2+1 is A002313(6).
a(n)== 6 or 68 (mod 74).
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
EXAMPLE
80 is in the sequence because 80^2+1= 37*173.
MATHEMATICA
lst={}; Do[If[FactorInteger[n^2+1][[1, 1]]==37, AppendTo[lst, n]], {n, 2, 4000}]; lst
p = 37; ps = Select[Range[p - 1], Mod[#, 4] != 3 && PrimeQ[#] &]; Select[Range[4000], Divisible[(nn = #^2 + 1), p] && ! Or @@ Divisible[nn, ps] &] (* Amiram Eldar, Aug 16 2019 *)
PROG
(Magma) [n: n in [2..4000] | PrimeDivisors(n^2+1)[1] eq 37]; // Bruno Berselli, Oct 08 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Michel Lagneau, Oct 08 2014
STATUS
approved