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 A213830 #16 Jun 17 2017 03:06:27
%S A213830 2,18,78,230,540,1092,1988,3348,5310,8030,11682,16458,22568,30240,
%T A213830 39720,51272,65178,81738,101270,124110,150612,181148,216108,255900,
%U A213830 300950,351702,408618,472178,542880,621240
%N A213830 Antidiagonal sums of the convolution array A213828.
%C A213830 Every term is even.
%H A213830 Clark Kimberling, <a href="/A213830/b213830.txt">Table of n, a(n) for n = 1..1000</a>
%H A213830 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).
%F A213830 a(n) = (2*n + n^2 + 2*n^3 + 3*n^4)/4.
%F A213830 a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5).
%F A213830 G.f.: f(x)/g(x), where f(x) = 2*x*(1 + 4*x + 4*x^2) and g(x) = (1-x)^5.
%t A213830 (See A213828.)
%t A213830 LinearRecurrence[{5,-10,10,-5,1},{2,18,78,230,540},30] (* _Harvey P. Dale_, Jan 11 2015 *)
%Y A213830 Cf. A213828.
%K A213830 nonn,easy
%O A213830 1,1
%A A213830 _Clark Kimberling_, Jul 04 2012