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 A253716 #8 Jan 05 2017 18:56:59
%S A253716 1,16322041,4145734153,67933251842771953,17254778510170993681,
%T A253716 282742011610770921096804841,71815357774355276244995175961,
%U A253716 1176788140728629029198108610250463201,298899554649081431834808455098428958753,4897858370145334123819452782766901335994312153
%N A253716 Hexagonal numbers (A000384) which are also centered heptagonal numbers (A069099).
%H A253716 Colin Barker, <a href="/A253716/b253716.txt">Table of n, a(n) for n = 1..208</a>
%H A253716 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,4162056194,0,-1).
%F A253716 a(n) = 4162056194*a(n-2)-a(n-4).
%F A253716 G.f.: -x*(x-1)*(x^2+16322042*x+1) / ((x^2-64514*x+1)*(x^2+64514*x+1)).
%e A253716 16322041 is in the sequence because it is the 2857th hexagonal number and the 2160th centered heptagonal number.
%t A253716 LinearRecurrence[{0,4162056194,0,-1},{1,16322041,4145734153,67933251842771953},20] (* _Harvey P. Dale_, Jan 05 2017 *)
%o A253716 (PARI) Vec(-x*(x-1)*(x^2+16322042*x+1)/((x^2-64514*x+1)*(x^2+64514*x+1)) + O(x^100))
%Y A253716 Cf. A000384, A069099, A253714, A253715.
%K A253716 nonn,easy
%O A253716 1,2
%A A253716 _Colin Barker_, Jan 10 2015