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A327373
BII-numbers of complete simple graphs.
1
0, 1, 4, 52, 2868, 9112372, 141334497921844, 39614688284139543691484924724, 3138550868424102398255194438067307501961665532948002835252, 19701003098197239607207513568280927372312554341759233318802451615112823176074440555010583132712036457851366790597428
OFFSET
0,3
COMMENTS
A binary index of n is any position of a 1 in its reversed binary expansion. The binary indices of n are row n of A048793. We define the set-system with BII-number n to be obtained by taking the binary indices of each binary index of n. Every set-system (finite set of finite nonempty sets) has a different BII-number. For example, 18 has reversed binary expansion (0,1,0,0,1), and since the binary indices of 2 and 5 are {2} and {1,3} respectively, the BII-number of {{2},{1,3}} is 18. Elements of a set-system are sometimes called edges.
MATHEMATICA
Table[If[n==1, 1, Total[2^(Total[2^#]/2&/@Subsets[Range[n], {2}])]/2], {n, 0, 10}]
CROSSREFS
BII-numbers of uniform set-systems are A326783.
BII-numbers of maximal uniform set-systems are A327080.
BII-numbers of maximal uniform normal set-systems are A327081.
Sequence in context: A355612 A317829 A327234 * A193914 A288490 A219160
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 04 2019
STATUS
approved