OFFSET
1,1
COMMENTS
From Robert Israel, Mar 29 2020: (Start)
All terms are even.
Contains all terms of A005574 that are even but not divisible by 4. (End)
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
28 is in the sequence because 28^2 + 1 = 5*157 and {5,157} == 5 (mod 8).
MAPLE
with(numtheory):for n from 1 to 300 do:x:=factorset(n^2+1):n1:=nops(x):s1:=0:for m from 1 to n1 do: if irem(x[m], 8)=5 then s1:=s1+1:else fi:od:if s1=n1 then printf(`%d, `, n):else fi:od:
MATHEMATICA
Select[Range[294], Union[Mod[Transpose[FactorInteger[#^2 + 1]][[1]], 8]] == {5} &] (* T. D. Noe, Aug 31 2012 *)
PROG
(Magma) [n: n in [1..300] | forall{PrimeDivisors(n^2+1)[i]: i in [1..#PrimeDivisors(n^2+1)] | PrimeDivisors(n^2+1)[i] mod 8 eq 5}]; // Bruno Berselli, Aug 30 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Aug 30 2012
STATUS
approved