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A123072
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Bishops on an 8n+1 X 8n+1 board (see Robinson paper for details).
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3
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2, 72, 7200, 1411200, 457228800, 221298739200, 149597947699200, 134638152929280000, 155641704786247680000, 224746621711341649920000, 396453040698806670458880000, 838894634118674914690990080000, 2097236585296687286727475200000000, 6115541882725140128097317683200000000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n) = A001700(n-1) * A010050(n). [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 16 2010]
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REFERENCES
| R. W. Robinson, Counting arrangements of bishops, pp. 198-214 of Combinatorial Mathematics IV (Adelaide 1975), Lect. Notes Math., 560 (1976). [The sequence zeta(2k+1).]
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FORMULA
| a(n) = (((2*n)! / n!)^2) / 2. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 16 2010]
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MAPLE
| For Maple program see A005635.
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CROSSREFS
| Cf. A173331. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Feb 16 2010]
Sequence in context: A179957 A174582 A051443 * A099681 A062082 A067689
Adjacent sequences: A123069 A123070 A123071 * A123073 A123074 A123075
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Sep 28 2006
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