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 A145123 #18 Jan 06 2024 00:57:45
%S A145123 1,301,90901,27451801,8290353001,2503659154501,756096774306301,
%T A145123 228338722181348401,68957538001992910801,20824948137879677713501,
%U A145123 6289065380101660676566501,1899276919842563644645369801
%N A145123 Numbers n such that there exists x in N : (x+1)^3-x^3=19*n^2.
%H A145123 Vincenzo Librandi, <a href="/A145123/b145123.txt">Table of n, a(n) for n = 1..100</a>
%H A145123 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (302,-1).
%F A145123 a(n+2) = 302*a(n+1)-a(n).
%F A145123 G.f.: -x*(-1+x) / ( 1-302*x+x^2 ). - _R. J. Mathar_, Nov 27 2011
%e A145123 a(1)=1 because 3^3-2^3=19*1.
%t A145123 CoefficientList[Series[(1 - x)/(1 - 302 x + x^2), {x, 0, 20}], x] (* _Vincenzo Librandi_, Oct 18 2014 *)
%o A145123 (PARI) Vec(-x*(-1+x)/(1-302*x+x^2) + O(x^30)) \\ _Colin Barker_, Oct 18 2014
%Y A145123 Cf. A145124.
%K A145123 easy,nonn
%O A145123 1,2
%A A145123 _Richard Choulet_, Oct 02 2008
%E A145123 Editing and more terms from _Colin Barker_, Oct 18 2014