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 A155612 #13 Oct 07 2015 11:15:01 %S A155612 1,5,41,317,2321,16565,116921,821357,5758241,40333925,282416201, %T A155612 1977149597,13840755761,96887416085,678218289881,4747547161037, %U A155612 33232887522881,232630384847045,1628413210489961,11398894023111677 %N A155612 7^n - 3^n + 1. %H A155612 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (11,-31,21). %F A155612 G.f.: 1/(1-7*x)-1/(1-3*x)+1/(1-x). %F A155612 E.g.f.: e^(7*x)-e^(3*x)+e^x. %F A155612 a(n) = 10*a(n-1)-21*a(n-2)+12 with a(0)=1, a(1)=5. - _Vincenzo Librandi_, Jul 21 2010 %o A155612 (PARI) a(n)=7^n-3^n+1 \\ _Charles R Greathouse IV_, Oct 07 2015 %Y A155612 Cf. A155596, A155597, A155598, A155599, A155600, A155601, A155602, A155603, A155604, A155605, A155606, A155607, A155608, A155609, A155610, A155611. %K A155612 nonn,easy %O A155612 0,2 %A A155612 _Mohammad K. Azarian_, Jan 26 2009