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 A204419 #14 Apr 03 2023 10:36:12
%S A204419 0,1819380158564160,117124856755987405647781716823680,
%T A204419 7540058082713667504003446125203741470945194284480,
%U A204419 485400601250164750241979240919394389707542655611270208094258863360
%N A204419 y-values in the solutions to x^2 - 313*y^2 = 1.
%D A204419 A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1996, p. 248.
%H A204419 G. L. Honaker, Jr. and Chris Caldwell, <a href="https://t5k.org/curios/cpage/40.html">Prime Curios! 313</a>
%H A204419 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (64376241658269698, -1).
%F A204419 a(n) = 64376241658269698*a(n-1) - a(n-2) with a(1) = 0 and a(2) = 1819380158564160.
%F A204419 G.f.: 1819380158564160*x^2/(1 - 64376241658269698*x + x^2).
%t A204419 LinearRecurrence[{64376241658269698, -1}, {0, 1819380158564160}, 5]
%o A204419 (Magma) I:=[0,1819380158564160]; [n le 2 select I[n] else 64376241658269698*Self(n-1)-Self(n-2): n in [1..10]]; // _Vincenzo Librandi_, May 16 2015
%Y A204419 Cf. A041591, A082393.
%K A204419 nonn,easy
%O A204419 1,2
%A A204419 _Arkadiusz Wesolowski_, Jan 15 2012