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 A213846 #15 Jun 17 2017 03:06:27 %S A213846 3,23,90,250,565,1113,1988,3300,5175,7755,11198,15678,21385,28525, %T A213846 37320,48008,60843,76095,94050,115010,139293,167233,199180,235500, %U A213846 276575,322803,374598,432390,496625,567765 %N A213846 Antidiagonal sums of the convolution array A213844. %H A213846 Clark Kimberling, <a href="/A213846/b213846.txt">Table of n, a(n) for n = 1..1000</a> %H A213846 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1). %F A213846 a(n) = n*(1 + n)*(1 - 2*n + 4*n^2)/6. %F A213846 a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5). %F A213846 G.f.: f(x)/g(x), where f(x) = x*(3 + 8*x + 5*x^2) and g(x) = (1-x)^5. %t A213846 (See A213846.) %Y A213846 Cf. A213846. %K A213846 nonn,easy %O A213846 1,1 %A A213846 _Clark Kimberling_, Jul 05 2012