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 A060069 #9 Jan 31 2020 14:34:57
%S A060069 1,0,0,0,2,82194,9185157387760082,
%T A060069 5573096894405951375691132323893805593,
%U A060069 47933892393105239218152796441416602126447041437452022947424986090407628
%N A060069 Number of n-block T_0-tricoverings.
%C A060069 A covering of a set is a tricovering if every element of the set is covered by exactly three blocks of the covering; A covering of a set is a T_0-covering if for every two distinct elements of the set there exists a block of the covering containing one but not the other element.
%D A060069 I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, John Wiley and Sons, N.Y., 1983.
%H A060069 Andrew Howroyd, <a href="/A060069/b060069.txt">Table of n, a(n) for n = 0..15</a>
%F A060069 E.g.f. for n-block T_0-tricoverings of a k-set is exp(-x+1/2*x^2+1/3*x^3*y)*Sum_{i=0..inf} (1+y)^binomial(i, 3)*exp(-1/2*x^2*(1+y)^i)*x^i/i!.
%Y A060069 Column sums of A059530.
%Y A060069 Cf. A060051, A060053, A060070, A060486.
%K A060069 nonn
%O A060069 0,5
%A A060069 _Vladeta Jovovic_, Feb 19 2001