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 A140431 #13 Jun 13 2015 00:52:38 %S A140431 0,2,2,12,22,92,222,772,2102,6732,19342,59732,175782,534172,1588862, %T A140431 4793892,14327062,43090412,129052782,387595252,1161911942,3487483452, %U A140431 10458955102,31383855812,94137586422,282440721292,847266239822 %N A140431 2*A094555(n). %H A140431 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (2,5,-6). %F A140431 b(n) = A091002(n-1); b(n+1)-3b(n)= A077925(n-2), where b(n)=floor(a(n)/10). %F A140431 a(n) = (1-(-2)^n+3^n)/3 for n>0. a(n) = 2*a(n-1)+5*a(n-2)-6*a(n-3) for n>3. G.f.: 2*x*(1-x-x^2)/((1-x)*(1+2*x)*(1-3*x)). [_Colin Barker_, Sep 21 2012] %K A140431 nonn,walk,easy %O A140431 0,2 %A A140431 _Paul Curtz_, Jun 19 2008 %E A140431 Edited and extended by _R. J. Mathar_, Aug 02 2008