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 A224509 #7 Jun 13 2015 00:54:38 %S A224509 1,3,10,35,125,451,1637,5965,21794,79781,292468,1073296,3941950, %T A224509 14486721,53264010,195909180,720769621,2652351034,9761957789, %U A224509 35933354194,132282020709,487008295675,1793068462212,6602016250702,24309222706566,89511103102442 %N A224509 Expansion of (1-x)*(1-2*x)*(1-3*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5). %C A224509 A diagonal of the square array A223968. %H A224509 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (9,-28,35,-15,1) %F A224509 a(n) = A223968(n+1,n). %F A224509 G.f.: (1-x)*(1-2*x)*(1-3*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5). %F A224509 a(n) = 9*a(n-1) - 28*a(n-2) + 35*a(n-3) - 15*a(n-4) + a(n-5) with a(0) = 1, a(1) = 3, a(2) = 10, a(3) = 35, a(4) = 125. %Y A224509 Cf. A223968 %K A224509 nonn,easy %O A224509 0,2 %A A224509 _Philippe Deléham_, Apr 08 2013