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 A147839 #10 Jan 03 2024 08:44:51
%S A147839 1,7,56,455,3703,30142,245357,1997219,16257472,132336715,1077228131,
%T A147839 8768696174,71377668649,581018144623,4729519621064,38498549577215,
%U A147839 313380308847487,2550932932586878,20764734231349493,169026077554037291
%N A147839 a(n)=9*a(n-1)-7*a(n-2), a(0)=1, a(1)=7 .
%H A147839 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (9,-7).
%F A147839 a(n)=Sum_{k, 0<=k<=n}A147703(n,k)*6^k . G.f.: (1-2x)/(1-9x+7*x^2).
%F A147839 a(n)= ((53+5*sqrt(53))/106)*(4.5+0.5*sqrt(53))^n + ((53-5*sqrt(53))/106)*(4.5-0.5*sqrt(53))^n [From _Richard Choulet_, Nov 20 2008]
%t A147839 LinearRecurrence[{9,-7},{1,7},30] (* _Harvey P. Dale_, Nov 30 2019 *)
%K A147839 nonn
%O A147839 0,2
%A A147839 _Philippe Deléham_, Nov 14 2008