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 A155589 #16 Jul 30 2024 07:03:08
%S A155589 1,7,39,223,1311,7807,46719,280063,1679871,10078207,60467199,
%T A155589 362799103,2176786431,13060702207,78364180479,470185017343,
%U A155589 2821109972991,16926659575807,101559956930559,609359740534783,3656158441111551,21936950642475007,131621703846461439
%N A155589 a(n) = 6^n + 2^n - 1.
%H A155589 Paolo Xausa, <a href="/A155589/b155589.txt">Table of n, a(n) for n = 0..1000</a>
%H A155589 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (9,-20,12).
%F A155589 G.f.: 1/(1-6*x)+1/(1-2*x)-1/(1-x).
%F A155589 E.g.f.: exp(6*x)+exp(2*x)-exp(x).
%F A155589 a(n) = 8*a(n-1)-12*a(n-2)-5 with a(0) = 1, a(1) = 7. - _Vincenzo Librandi_, Jul 21 2010
%t A155589 Table[6^n + 2^n - 1, {n, 0, 25}] (* _Paolo Xausa_, Jul 30 2024 *)
%o A155589 (PARI) a(n)=6^n+2^n-1 \\ _Charles R Greathouse IV_, Jun 11 2015
%Y A155589 Cf. A074501, A074600, A005057, A005056, A099393, A155588.
%K A155589 nonn,easy
%O A155589 0,2
%A A155589 _Mohammad K. Azarian_, Jan 24 2009