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A122801 Number of labeled bipartite graphs on 2n vertices having equal parts and no isolated vertices. 2
1, 1, 21, 2650, 1452605, 3149738046, 26503552820514, 868081172737564500, 111606080497500509325405, 56762846667123360827351083510, 114847831981827229530824587617895286, 927685362544629192461621864598358779955500, 29976424929810726580224613882836823991388901138994 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..50

FORMULA

For n>0, a(n) = A001700(n-1) * A048291(n) = A052332(2n) - A122802(2n).

PROG

(PARI) { A122801(n) = binomial(2*n-1, n) * sum(k=0, n, binomial(n, k) * (-1)^k * (2^(n-k)-1)^n ); }

CROSSREFS

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

KEYWORD

nonn

AUTHOR

Max Alekseyev, Sep 11 2006

EXTENSIONS

Terms a(11) and beyond from Andrew Howroyd, Nov 07 2019

STATUS

approved

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Last modified May 27 14:33 EDT 2022. Contains 354097 sequences. (Running on oeis4.)