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 A155604 #25 Aug 21 2024 12:26:29
%S A155604 1,8,44,242,1376,8018,47384,282122,1686176,10097378,60525224,
%T A155604 362974202,2177313776,13062288338,78368947064,470199333482,
%U A155604 2821152954176,16926788584898,101560344088904,609360902271962,3656161926847376
%N A155604 a(n) = 6^n + 3^n - 1.
%H A155604 Paolo Xausa, <a href="/A155604/b155604.txt">Table of n, a(n) for n = 0..1000</a>
%H A155604 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (10,-27,18).
%F A155604 G.f.: 1/(1-6*x)+1/(1-3*x)-1/(1-x).
%F A155604 E.g.f.: exp(6*x)+exp(3*x)-exp(x).
%F A155604 a(n) = 9*a(n-1)-18*a(n-2)-10 with a(0) = 1, a(1) = 8. - _Vincenzo Librandi_, Jul 21 2010
%t A155604 Table[6^n + 3^n - 1, {n, 0, 25}] (* _Paolo Xausa_, Aug 21 2024 *)
%o A155604 (PARI) a(n)=6^n+3^n-1 \\ _Charles R Greathouse IV_, Jun 11 2015
%Y A155604 Cf. A074501, A020515, A155588, A155590, A155592, A155593, A155594, A155596, A155597, A155598, A155599, A155600, A155601, A155602, A155603.
%K A155604 nonn,easy
%O A155604 0,2
%A A155604 _Mohammad K. Azarian_, Jan 25 2009