Search: id:A072445
Results 1-1 of 1 results found.

%I A072445
%S A072445 1,1,4,40,3044,26012090
%N A072445 Number of subsets S of the power set P{1,2,...,n} such that: {1}, {2},
               ..., {n} are all elements of S; {1,2,...,n} is an element of S; if 
               X and Y are elements of S and X and Y have a non-empty intersection, 
               then the union of X and Y is an element of S. The sets S are counted 
               modulo permutations on the elements 1,2,...,n.
%H A072445 Wim van Dam, <a href="http://www.cs.berkeley.edu/~vandam/subpowersets/
               sequences.html">Sub Power Set Sequences</a>
%e A072445 a(3)=4 because of the 4 sets: {{1}, {2}, {3}, {1, 2, 3}}; {{1}, {2}, 
               {3}, {1, 2}, {1, 2, 3}}; {{1}, {2}, {3}, {1, 2}, {1, 3}, {1, 2, 3}}; 
               {{1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1, 2, 3}}.
%Y A072445 Cf. A072444, A072446, A072447.
%Y A072445 Sequence in context: A111846 A102922 A139688 this_sequence A000841 A059918 
               A002677
%Y A072445 Adjacent sequences: A072442 A072443 A072444 this_sequence A072446 A072447 
               A072448
%K A072445 nonn
%O A072445 1,3
%A A072445 Wim van Dam (vandam(AT)cs.berkeley.edu), Jun 18 2002

Search completed in 0.001 seconds