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1, 9, 75, 763, 9495, 140151, 2390479, 46206735, 997313823, 23758664095, 618884638911, 17492190577599, 532985208200575, 17411277367391103, 606917269909048575, 22481059424730751231, 881687990282453393919
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| a(n) is the number of sets of disjoint pairs that can be chosen from 2*n items. - Ron Zeno (rzeno(AT)hotmail.com), Feb 06 2002
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CROSSREFS
| Sequence in context: A190983 A136659 A126965 * A080254 A190916 A161736
Adjacent sequences: A066219 A066220 A066221 * A066223 A066224 A066225
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Dec 19 2001
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EXTENSIONS
| More terms from Frank Ellermann, Jan 01, 2002
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