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 A155199 #24 Jan 03 2024 08:47:55
%S A155199 1,9,90,909,9180,92709,936270,9455409,95490360,964359009,9739080450,
%T A155199 98355163509,993290715540,10031262318909,101305913904630,
%U A155199 1023090401365209,10332209927556720,104345189676932409,1053784106696880810,10642186256645740509,107475646673154285900
%N A155199 a(n) = 10*a(n-1) + a(n-2), n > 2 ; a(0) = 1, a(1) = 9, a(2) = 90.
%H A155199 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (10,1).
%F A155199 G.f.: (1 - x - x^2)/(1 - 10*x - x^2).
%F A155199 a(n) = Sum_{k=0..n} A155161(n,k)*9^k. - _Philippe Deléham_, Feb 08 2012
%F A155199 E.g.f.: 1 + 9*exp(5*x)*sinh(sqrt(26)*x)/sqrt(26). - _Stefano Spezia_, Mar 01 2023
%t A155199 LinearRecurrence[{10,1},{1,9,90},20] (* _Harvey P. Dale_, Dec 20 2022 *)
%Y A155199 Cf. A001019, A155161.
%K A155199 nonn,easy
%O A155199 0,2
%A A155199 _Philippe Deléham_, Jan 21 2009