%I
%S 1,2,6,28,330,28960,216562364,5592326182940100
%N Number of nonisomorphic systems enumerated by A102895.
%C Also the number of nonisomorphic sets of sets with {} that are closed under intersection. Also the number of nonisomorphic setsystems (without {}) covering n + 1 vertices and closed under intersection.  _Gus Wiseman_, Aug 05 2019
%H M. Habib and L. Nourine, <a href="https://doi.org/10.1016/j.disc.2004.11.010">The number of Moore families on n = 6</a>, Discrete Math., 294 (2005), 291296.
%F a(n > 0) = 2 * A108798(n).
%e From _Gus Wiseman_, Aug 02 2019: (Start)
%e Nonisomorphic representatives of the a(0) = 1 through a(3) = 28 sets of sets with {} that are closed under intersection:
%e {} {} {} {}
%e {}{1} {}{1} {}{1}
%e {}{12} {}{12}
%e {}{1}{2} {}{123}
%e {}{2}{12} {}{1}{2}
%e {}{1}{2}{12} {}{1}{23}
%e {}{2}{12}
%e {}{3}{123}
%e {}{1}{2}{3}
%e {}{23}{123}
%e {}{1}{2}{12}
%e {}{1}{3}{23}
%e {}{2}{3}{123}
%e {}{3}{13}{23}
%e {}{1}{23}{123}
%e {}{3}{23}{123}
%e {}{1}{2}{3}{23}
%e {}{1}{2}{3}{123}
%e {}{2}{3}{13}{23}
%e {}{1}{3}{23}{123}
%e {}{2}{3}{23}{123}
%e {}{3}{13}{23}{123}
%e {}{1}{2}{3}{13}{23}
%e {}{1}{2}{3}{23}{123}
%e {}{2}{3}{13}{23}{123}
%e {}{1}{2}{3}{12}{13}{23}
%e {}{1}{2}{3}{13}{23}{123}
%e {}{1}{2}{3}{12}{13}{23}{123}
%e (End)
%Y Except a(0) = 1, first differences of A193675.
%Y The connected case (i.e., with maximum) is A108798.
%Y The same for union instead of intersection is (also) A108798.
%Y The labeled version is A102895.
%Y The case also closed under union is A326898.
%Y The covering case is A326883.
%Y Cf. A001930, A102894, A102896, A102897, A193674, A326880, A326881.
%K nonn,more
%O 0,2
%A _Don Knuth_, Jul 01 2005
%E a(6) added (using A193675) by _N. J. A. Sloane_, Aug 02 2011
%E Changed a(0) from 2 to 1 by _Gus Wiseman_, Aug 02 2019
%E a(7) added (using A108798) by _Andrew Howroyd_, Aug 10 2019
