OFFSET
0,2
COMMENTS
Related to period-1 continued fractions [z,z,z,...].
LINKS
Enrique PĂ©rez Herrero, Table of n, a(n) for n = 0..5000
EXAMPLE
a(7)=2 since 7^2+1 = 50 = 25*2 = (5^2)*2.
MAPLE
A:= proc(n)
local F;
F:= select(t -> t[2]::odd, ifactors(n^2+1)[2]);
mul(t[1], t=F)
end proc:
map(A, [$0..100]); # Robert Israel, Jun 18 2015
MATHEMATICA
Table[Times @@ Flatten[Table[#1, {#2}] & @@@ Select[FactorInteger[n^2 + 1], OddQ@ Last@ # &]], {n, 120}] (* Michael De Vlieger, Jun 19 2015 *)
PROG
(PARI) a(n) = core(n^2+1); \\ Michel Marcus, Jun 18 2015
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Marc LeBrun, Jan 25 2001
STATUS
approved