Search: id:A072444
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%I A072444
%S A072444 1,2,6,47,3095,26015236
%N A072444 Number of subsets S of the power set P{1,2,...,n} such that: {1}, {2},
               ..., {n} are all elements 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 A072444 Wim van Dam, <a href="http://www.cs.berkeley.edu/~vandam/subpowersets/
               sequences.html">Sub Power Set Sequences</a>
%e A072444 a(3)=6 because of the 6 sets: {{1}, {2}, {3}}; {{1}, {2}, {3}, {1, 2}}; 
               {{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 A072444 Cf. A072445, A072446, A072447.
%Y A072444 Sequence in context: A001587 A078537 A145502 this_sequence A052596 A098710 
               A052614
%Y A072444 Adjacent sequences: A072441 A072442 A072443 this_sequence A072445 A072446 
               A072447
%K A072444 nonn
%O A072444 1,2
%A A072444 Wim van Dam (vandam(AT)cs.berkeley.edu), Jun 18 2002

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