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 A249863 #16 Sep 08 2022 08:46:10
%S A249863 1,26,627,15028,360005,8623758,206577463,4948449896,118537401609,
%T A249863 2839498396930,68018625641339,1629348845225244,39030157319430733,
%U A249863 934945996889162102,22396118210466108735,536486719624549884112
%N A249863 Chebyshev S polynomial (A049310) evaluated at x = 26/7 and multiplied by powers of 7 (A000420).
%C A249863 This sequence appears in the solution of the curvature sequence of the touching circle and chord example given by _Kival Ngaokrajang_ in A249458. See also the pair A249864(n) and a(n-1), with a(-1) = 0, for which details are given in A249864.
%H A249863 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (26,-49)
%H A249863 <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials</a>
%F A249863 a(n) = 7^n*S(n, 26/7) with Chebyshev's S polynomial (for S see the coefficient triangle A049310).
%F A249863 O.g.f.: 1/(1 - 26*x + (7*x)^2).
%F A249863 a(n) = 26*a(n-1) - 49*a(n-2), a(-1) = 0, a(0) = 1 .
%t A249863 LinearRecurrence[{26,-49},{1,26},20] (* _Harvey P. Dale_, Jun 30 2017 *)
%o A249863 (Magma) I:=[1,26]; [n le 2 select I[n] else 26*Self(n-1)-49*Self(n-2): n in [1..40]]; // _Vincenzo Librandi_, Nov 09 2014
%Y A249863 Cf. A000420, A049310, A249864, A248163.
%K A249863 nonn,easy
%O A249863 0,2
%A A249863 _Wolfdieter Lang_, Nov 09 2014