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Search: id:A122749
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| A122749 |
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Bishops on an n X n board (see Robinson paper for details). |
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+0
2
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| 4, 2, 16, 44, 256, 768, 5184, 25344, 186624, 996480, 8294400, 57888000, 530841600, 4006195200, 40642560000, 367408742400, 4064256000000, 39358255104000, 474054819840000, 5254107586560000, 68263894056960000, 804207665479680000, 11242684107325440000
(list; graph; listen)
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OFFSET
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2,1
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REFERENCES
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R. W. Robinson, Counting arrangements of bishops, pp. 198-214 of Combinatorial Mathematics IV (Adelaide 1975), Lect. Notes Math., 560 (1976). (E_n, n >= 2)
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MAPLE
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E:=proc(n) local k; if n mod 2 = 0 then k := n/2; if k mod 2 = 0 then RETURN( (k!*(k+2)/2)^2 ); else RETURN( ((k-1)!*(k+1)^2/2)^2 ); fi; else k := (n-1)/2; if k mod 2 = 0 then RETURN( ((k!)^2/12)*(3*k^3+16*k^2+18*k+8) ); else RETURN( ((k-1)!*(k+1)!/12)*(3*k^3+13*k^2-k-3) ); fi; fi; end;
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CROSSREFS
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Sequence in context: A038232 A084623 A137393 this_sequence A074676 A117692 A052966
Adjacent sequences: A122746 A122747 A122748 this_sequence A122750 A122751 A122752
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KEYWORD
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nonn
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AUTHOR
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njas, Sep 25 2006
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