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 A155196 #17 Jan 03 2024 08:47:48
%S A155196 1,6,42,300,2142,15294,109200,779694,5567058,39749100,283810758,
%T A155196 2026424406,14468781600,103307895606,737624050842,5266676251500,
%U A155196 37604357811342,268497180930894,1917084624327600,13688089551224094
%N A155196 a(n)=7*a(n-1)+a(n-2), n>2 ; a(0)=1, a(1)=6, a(2)=42 .
%H A155196 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (7, 1).
%F A155196 G.f.: (1-x-x^2)/(1-7*x-x^2).
%F A155196 a(n) = Sum_{k, 0<=k<=n} A155161(n,k)*6^k. - _Philippe Deléham_, Feb 08 2012
%t A155196 Join[{1},LinearRecurrence[{7,1},{6,42},20]] (* _Harvey P. Dale_, Sep 04 2014 *)
%K A155196 nonn,easy
%O A155196 0,2
%A A155196 _Philippe Deléham_, Jan 21 2009