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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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1
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1, 1, 21, 2650, 1452605, 3149738046, 26503552820514, 868081172737564500, 111606080497500509325405, 56762846667123360827351083510, 114847831981827229530824587617895286
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| For n>0, a(n) = A001700(n-1) * A048291(n) = A052332(2n) - A122802(2n)
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PROG
| (PARI) { a(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
| Cf. A122802, A048291, A052332, A001831, A002031, A047863, A001700.
Sequence in context: A068254 A144853 A131314 * A099680 A184367 A114934
Adjacent sequences: A122798 A122799 A122800 * A122802 A122803 A122804
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KEYWORD
| nonn
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AUTHOR
| Max Alekseyev (maxale(AT)gmail.com), Sep 11 2006
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