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 A140420 #8 Jul 28 2015 15:53:39 %S A140420 0,1,3,13,45,151,483,1513,4665,14251,43263,130813,394485,1187551, %T A140420 3570843,10728913,32219505,96724051,290303223,871171813,2614039725, %U A140420 7843167751,23531600403,70598995513,211805375145,635432902651 %N A140420 Binomial transform of 0, 1, 1, 7, 7, 31, 31, ..., zero followed by duplicated A083420. %H A140420 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (5, -5, -5, 6). %F A140420 a(n+1)-3a(n) = A099430(n). %F A140420 O.g.f.: (3x^2-2x+1)x/((2x-1)(1+x)(3x-1)(1-x)). - _R. J. Mathar_, Jul 10 2008 %F A140420 a(n)+a(n+1)=A126644(n). - _R. J. Mathar_, Jul 10 2008 %K A140420 nonn %O A140420 0,3 %A A140420 _Paul Curtz_, Jun 18 2008, corrected Jun 23 2008 %E A140420 More terms from _R. J. Mathar_, Jul 10 2008