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 A087448 #8 Jun 13 2015 00:51:08 %S A087448 1,2,7,26,93,322,1091,3642,12025,39362,127935,413338,1328597,4251522, %T A087448 13551739,43046714,136314609,430467202,1355971703,4261625370, %U A087448 13366006861,41841412802,130754415027,407953774906,1270932914153 %N A087448 3^(n-1)(n+3)/2-(n-1)/2. %C A087448 Binomial transform of A087447. Second binomial transform of 1,0,3,0,5,0,7,... (A005408). %H A087448 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (8,-22,24,-9). %F A087448 G.f.: (1-2*x)*(1-4*x+5*x^2)/((1-x)^2*(1-3*x)^2). [_Colin Barker_, Mar 18 2012] %K A087448 easy,nonn %O A087448 0,2 %A A087448 _Paul Barry_, Sep 05 2003