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In mathematics and especially in combinatorics, a plane partition is a two-dimensional array of nonnegative integers (with positive integer indices ''i'' and ''j'') that is nonincreasing in both indices, that is, that satisfies : for all ''i'' and ''j'', and for which only finitely many of the ''n''''i'',''j'' are nonzero. A plane partitions may be represented visually by the placement of a stack of unit cubes above the point (''i'',''j'') in the plane, giving a three-dimensional solid like the one shown at right. The ''sum'' of a plane partition is : and PL(''n'') denotes the number of plane partitions with sum ''n''. For example, there are six plane partitions with sum 3: : so PL(3) = 6. (Here the plane partitions are drawn using matrix indexing for the coordinates and the entries equal to 0 are suppressed for readability.) == Ferrers diagrams for plane partitions == Another representation for plane partitions is in the form of Ferrers diagrams. The Ferrers diagram of a plane partition of is a collection of points or ''nodes'', , with satisfying the condition:〔A. O. L. Atkin, P. Bratley, I. G. Macdonald and J. K. S. McKay, Some computations for ''m''-dimensional partitions, Proc. Camb. Phil. Soc., 63 (1967), 1097–1100.〕 :Condition FD: If the node , then so do all the nodes with for all . Replacing every node of a plane partition by a unit cube with edges aligned with the axes leads to the ''stack of cubes'' representation for the plane partition. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Plane partition」の詳細全文を読む スポンサード リンク
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