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Search: id:A048194
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| A048194 |
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Total number of split graphs (chordal + chordal complement) on n vertices. |
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+0
10
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| 1, 2, 4, 9, 21, 56, 164, 557, 2223, 10766, 64956, 501696, 5067146, 67997750, 1224275498, 29733449510, 976520265678, 43425320764422, 2616632636247976, 213796933371366930, 23704270652844196754, 3569464106212250952762
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Also number of bipartite graphs with n vertices and no isolated vertices in distinguished bipartite block, up to isomorphism; so a(n) equals first differences of A049312 - Vladeta Jovovic (vladeta(AT)eunet.rs), Jun 17 2000
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LINKS
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Gordon Royle, Counting set covers and split graphs, J. Integer Seqs., Vol. 3 (2000), #00.2.6
Vladeta Jovovic, Binary matrices up to row and column permutations.
Index entries for sequences related to posets
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CROSSREFS
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Cf. A048192-A048194, A055080.
Detlef Pauly remarks that this is the unlabeled analogue of A001831.
Sequence in context: A148074 A130866 A123458 this_sequence A148075 A058718 A148076
Adjacent sequences: A048191 A048192 A048193 this_sequence A048195 A048196 A048197
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KEYWORD
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nonn,nice,easy
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AUTHOR
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Gordon Royle (gordon(AT)maths.uwa.edu.au)
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