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 A213775 #15 Feb 19 2024 03:11:27 %S A213775 1,11,38,97,213,432,833,1555,2838,5097,9045,15904,27761,48171,83174, %T A213775 143009,244997,418384,712465,1210195,2050966,3468681,5855333,9867072, %U A213775 16600993,27889547,46790438,78401185,131212533,219355632 %N A213775 Principal diagonal of the convolution array A213774. %H A213775 Clark Kimberling, <a href="/A213775/b213775.txt">Table of n, a(n) for n = 1..1000</a> %H A213775 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (4,-4,-2,4,0,-1). %F A213775 a(n) = 4*a(n-1) - 4*a(n-2) - 2*a(n-3) + 4*a(n-4) - a(n-6). %F A213775 G.f.: f(x)/g(x), where f(x) = x*(1 + 7*x - 2*x^2 - 9*x^3 - 5*x^4) and g(x) = (1 - 2*x + x^3 )^2. %t A213775 (See A213774.) %Y A213775 Cf. A213774, A213500. %K A213775 nonn,easy %O A213775 1,2 %A A213775 _Clark Kimberling_, Jun 21 2012