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 A365645 #12 Sep 17 2023 05:40:05
%S A365645 0,1,33,666,11110,166665,2333331,31111108,399999996,4999999995,
%T A365645 61111111105,733333333326,8666666666658,101111111111101,
%U A365645 1166666666666655,13333333333333320,151111111111111096,1699999999999999983,18999999999999999981,211111111111111111090,2333333333333333333310
%N A365645 a(n) = n*(1 + n)*(10^n - 1)/18.
%H A365645 Stefano Spezia, <a href="/A365645/b365645.txt">Table of n, a(n) for n = 0..990</a>
%H A365645 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (33,-393,1991,-3930,3300,-1000).
%F A365645 O.g.f.: x*(1 - 30*x^2 + 110*x^3)/((1 - x)^3*(1 - 10*x)^3).
%F A365645 E.g.f.: exp(x)*x*(20*exp(9*x)*(1 + 5*x) - 2 - x)/18.
%F A365645 a(n) = 33*a(n-1) - 393*a(n-2) + 1991*a(n-3) - 3930*a(n-4) + 3300*a(n-5) - 1000*a(n-6) for n > 5.
%t A365645 Table[n(1+n)(10^n-1)/18,{n,0,20}]
%Y A365645 Antidiagonal sums of A365644.
%K A365645 nonn,easy
%O A365645 0,3
%A A365645 _Stefano Spezia_, Sep 14 2023