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剛哥學數(shù)學新蟲 (小有名氣)
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[求助]
n級排列中逆序為2的排列有多少個?
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求指點,感激不盡 [ 發(fā)自手機版 http://www.gaoyang168.com/3g ] |
榮譽版主 (文壇精英)
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專家經(jīng)驗: +518 |
新蟲 (小有名氣)
榮譽版主 (文壇精英)
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專家經(jīng)驗: +518 |
新蟲 (小有名氣)
榮譽版主 (文壇精英)
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專家經(jīng)驗: +518 |
至尊木蟲 (著名寫手)
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http://en.wikipedia.org/wiki/Permutation: The number of permutations of n with k inversions is expressed by a Mahonian number,[12] it is the coefficient of Xk in the expansion of the product which is also known (with q substituted for X) as the q-factorial [n]q! . The expansion of the product appears in Necklace (combinatorics). http://oeis.org/A008302 A008302 Triangle of Mahonian numbers T(n,k): coefficients in expansion of Product_{i=0..n-1} (1+x+...+x^i), where k ranges from 0 to A000217(n-1). 82 1, 1, 1, 1, 2, 2, 1, 1, 3, 5, 6, 5, 3, 1, 1, 4, 9, 15, 20, 22, 20, 15, 9, 4, 1, 1, 5, 14, 29, 49, 71, 90, 101, 101, 90, 71, 49, 29, 14, 5, 1, 1, 6, 20, 49, 98, 169, 259, 359, 455, 531, 573, 573, 531, 455, 359, 259, 169, 98, 49, 20, 6, 1 google 來的, 錯了不要怪我. |

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