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 A213829 #11 Jun 17 2017 02:59:44 %S A213829 2,28,114,296,610,1092,1778,2704,3906,5420,7282,9528,12194,15316, %T A213829 18930,23072,27778,33084,39026,45640,52962,61028,69874,79536,90050, %U A213829 101452,113778,127064,141346,156660,173042 %N A213829 Principal diagonal of the convolution array A213828. %H A213829 Clark Kimberling, <a href="/A213829/b213829.txt">Table of n, a(n) for n = 1..1000</a> %H A213829 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1). %F A213829 a(n) = 2*(n - 3*n^2 + 3*n^3). %F A213829 a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4). %F A213829 G.f.: f(x)/g(x), where f(x) = 2*x*(1 + 10*x + 7*x^2) and g(x) = (1-x)^4. %t A213829 (See A213828.) %Y A213829 Cf. A213828. %K A213829 nonn,easy %O A213829 1,1 %A A213829 _Clark Kimberling_, Jul 04 2012