This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A059591 #15 Jun 20 2015 08:54:22
%S A059591 1,2,5,10,17,26,37,2,65,82,101,122,145,170,197,226,257,290,13,362,401,
%T A059591 442,485,530,577,626,677,730,785,842,901,962,41,1090,1157,1226,1297,
%U A059591 1370,5,1522,1601,2,1765,74,1937,2026,2117,2210,2305,2402,2501,2602
%N A059591 Squarefree part of n^2+1.
%C A059591 Related to period-1 continued fractions [z,z,z,...].
%H A059591 Enrique Pérez Herrero, <a href="/A059591/b059591.txt">Table of n, a(n) for n = 0..5000</a>
%F A059591 a(n) = A007913(n^2+1).
%F A059591 a(n)*A059592(n)^2 = n^2+1.
%e A059591 a(7)=2 since 7^2+1 = 50 = 25*2 = (5^2)*2.
%p A059591 A:= proc(n)
%p A059591 local F;
%p A059591 F:= select(t -> t[2]::odd, ifactors(n^2+1)[2]);
%p A059591 mul(t[1],t=F)
%p A059591 end proc:
%p A059591 map(A, [$0..100]); # _Robert Israel_, Jun 18 2015
%t A059591 Table[Times @@ Flatten[Table[#1, {#2}] & @@@ Select[FactorInteger[n^2 + 1], OddQ@ Last@ # &]], {n, 120}] (* _Michael De Vlieger_, Jun 19 2015 *)
%o A059591 (PARI) a(n) = core(n^2+1); \\ _Michel Marcus_, Jun 18 2015
%Y A059591 Cf. A007913, A059592, A000188.
%K A059591 easy,nonn
%O A059591 0,2
%A A059591 _Marc LeBrun_, Jan 25 2001