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 A213549 #20 Nov 20 2022 13:52:19
%S A213549 1,12,53,155,360,721,1302,2178,3435,5170,7491,10517,14378,19215,25180,
%T A213549 32436,41157,51528,63745,78015,94556,113597,135378,160150,188175,
%U A213549 219726,255087,294553,338430,387035,440696,499752,564553,635460
%N A213549 Principal diagonal of the convolution array A213548.
%H A213549 Clark Kimberling, <a href="/A213549/b213549.txt">Table of n, a(n) for n = 1..1000</a>
%H A213549 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (5,-10,10,-5,1).
%F A213549 G.f.: x*(1 + 7*x + 3*x^2)/(1 - x)^5.
%F A213549 a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5).
%F A213549 a(n) = (11*n^4 + 14*n^3 + n^2 - 2*n)/24 = n*(n+1)*(11*n^2 + 3*n - 2)/24.
%F A213549 a(n) = Sum_{i=1..n} (n-i+1)*A000217(n+i-1), see A213548. - _Bruno Berselli_, Oct 05 2016
%t A213549 (See A213548.)
%t A213549 LinearRecurrence[{5,-10,10,-5,1},{1,12,53,155,360},40] (* _Harvey P. Dale_, Nov 20 2022 *)
%Y A213549 Cf. A000217, A213500, A213548.
%K A213549 nonn,easy
%O A213549 1,2
%A A213549 _Clark Kimberling_, Jun 16 2012