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 A213850 #16 Feb 18 2024 07:58:37 %S A213850 1,3,10,20,42,70,120,180,275,385,546,728,980,1260,1632,2040,2565,3135, %T A213850 3850,4620,5566,6578,7800,9100,10647,12285,14210,16240,18600,21080, %U A213850 23936,26928,30345,33915,37962,42180,46930 %N A213850 Antidiagonal sums of the convolution array A213849. %H A213850 Clark Kimberling, <a href="/A213850/b213850.txt">Table of n, a(n) for n = 1..500</a> %H A213850 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (2,2,-6,0,6,-2,-2,1). %F A213850 a(n) = (n + 1)*(n + 2)*(3 - 3*(-1)^n + 8*n + 2*n^2)/96. %F A213850 a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5). %F A213850 G.f.: f(x)/g(x), where f(x) = x*(1 + x + 2*x^2) and g(x) = (1+x)^3*(1-x)^5. %t A213850 (See A213849.) %Y A213850 Cf. A213849. %K A213850 nonn,easy %O A213850 1,2 %A A213850 _Clark Kimberling_, Jul 05 2012