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A122801
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Number of labeled bipartite graphs on 2n vertices having equal parts and no isolated vertices.
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2
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1, 1, 21, 2650, 1452605, 3149738046, 26503552820514, 868081172737564500, 111606080497500509325405, 56762846667123360827351083510, 114847831981827229530824587617895286, 927685362544629192461621864598358779955500, 29976424929810726580224613882836823991388901138994
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history;
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internal format)
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OFFSET
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0,3
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LINKS
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Andrew Howroyd, Table of n, a(n) for n = 0..50
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FORMULA
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For n>0, a(n) = A001700(n-1) * A048291(n) = A052332(2n) - A122802(2n).
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PROG
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(PARI) { A122801(n) = binomial(2*n-1, n) * sum(k=0, n, binomial(n, k) * (-1)^k * (2^(n-k)-1)^n ); }
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CROSSREFS
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Cf. A122802, A048291, A052332, A001831, A002031, A047863, A001700.
Sequence in context: A131314 A225686 A221779 * A099680 A352086 A184367
Adjacent sequences: A122798 A122799 A122800 * A122802 A122803 A122804
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KEYWORD
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nonn
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AUTHOR
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Max Alekseyev, Sep 11 2006
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EXTENSIONS
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Terms a(11) and beyond from Andrew Howroyd, Nov 07 2019
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STATUS
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approved
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