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 A213565 #10 Jun 17 2017 03:53:57 %S A213565 1,21,127,467,1302,3038,6258,11754,20559,33979,53625,81445,119756, %T A213565 171276,239156,327012,438957,579633,754243,968583,1229074,1542794, %U A213565 1917510,2361710,2884635,3496311,4207581,5030137,5976552,7060312 %N A213565 Principal diagonal of the convolution array A213564. %H A213565 Clark Kimberling, <a href="/A213565/b213565.txt">Table of n, a(n) for n = 1..1000</a> %H A213565 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (6,-15,20,-15,6,-1). %F A213565 a(n) = (16*n^5 + 85*n^4 + 15*n^3 - 25*n^2 - n)/60. %F A213565 a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6). %F A213565 G.f.: x*(1 + 15*x + 16*x^2)/(1 - x)^6. %t A213565 (See A213564.) %Y A213565 Cf. A213564, A213500. %K A213565 nonn,easy %O A213565 1,2 %A A213565 _Clark Kimberling_, Jun 18 2012