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 A155616 #13 Oct 16 2015 14:59:54 %S A155616 1,8,40,188,880,4148,19720,94508,456160,2215268,10814200,53022428, %T A155616 260917840,1287811988,6371951080,31591319948,156882857920, %U A155616 780119322308,3883416742360,19348364235068,96466943268400,481235204714228 %N A155616 5^n + 4^n - 1. %H A155616 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (10,-29,20). %F A155616 G.f.: 1/(1-5*x)+1/(1-4*x)-1/(1-x). %F A155616 E.g.f.: e^(5*x)+e^(4*x)-e^x. %F A155616 a(n) = 9*a(n-1)-20*a(n-2)-12 with a(0)=1, a(1)=8 - _Vincenzo Librandi_, Jul 21 2010 %o A155616 (PARI) a(n)=5^n+4^n-1 \\ _Charles R Greathouse IV_, Oct 16 2015 %Y A155616 Cf. A155588, A155599, A155607, A155608, A155609, A155610, A155611, A155612, A155613, A155614, A155615. %K A155616 nonn,easy %O A155616 0,2 %A A155616 _Mohammad K. Azarian_, Jan 27 2009