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 A327248 #21 Mar 02 2023 07:18:47
%S A327248 6,210,1785,60639,915530,184030,14066106,80753867670,10973017315470,
%T A327248 372759573255306,351745902037915,11949006236698685,86466986871277074,
%U A327248 122261486084598,43869141307765893,35803482505852454889891,2162247909473892250092390,73452778286546376583337010
%N A327248 Squarefree part of A078522(n+1).
%C A327248 Also the squarefree part of (A001653(n+1)^2-1)/2 or of A002315(n)^2-1
%C A327248 Walsh shows that the system of simultaneous Pell equations x^2 - d*y^2 = z^2 - 2*d*y^2 = 1 has solutions in positive integers x, y, z if and only if d belongs to this sequence and, under the abc conjecture, this sequences grows exponentially.
%H A327248 P. G. Walsh, <a href="https://doi.org/10.4064/aa-82-1-69-76">On integer solutions to x^2 - dy^2 = 1, z^2 - 2dy^2 = 1</a>, Acta Arithmetica 82 (1997), 69-76.
%F A327248 a(n) = A007913(A078522(n+1)).
%e A327248 a(2) = 210 since A078522(3) = 840 = 210 * 2^2.
%o A327248 (PARI) a(n)={local(z=1+quadgen(8)); core(imag(z^(2*n+1))^2-1)}
%Y A327248 Cf. A007913, A001653, A002315, A078522.
%K A327248 nonn
%O A327248 1,1
%A A327248 _Tomohiro Yamada_, Sep 15 2019
%E A327248 Missing a(11) inserted and more terms from _Georg Fischer_, Mar 02 2023