4_7.htm
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<html><head><title>Untitled Document</title><meta http-equiv="Content-Type" content="text/html; charset=gb2312"><link rel="stylesheet" href="../style.css"></head><body bgcolor="#FFFFFF"><h1>4.7 母函数型式的Pólya定理</h1><p><img width=119 height=51 src="./4_7/image002.gif" align="middle"> 目标集[1,n]<br>m种颜色:b<sub>1</sub>,b<sub>2</sub>,…,b<sub>m</sub><br><img width=40 height=21 src="./4_7/image004.gif" align="middle">用<img width=419 height=29 src="./4_7/image006.gif" align="middle">代替<br>P(b<sub>1</sub>,b<sub>2</sub>,…,b<sub>m</sub>)以b<sub>1</sub>,b<sub>2</sub>,…,b<sub>m</sub>为变元的n次对称多项式。<br>令<img width=144 height=25 src="./4_7/image008.gif" align="middle"><br><img width=181 height=25 src="./4_7/image010.gif" align="middle"><br><img width=211 height=49 src="./4_7/image012.gif" align="middle"><br><img width=97 height=27 src="./4_7/image014.gif" align="middle"></p><p><b>[例1]</b>有3种不同颜色的珠子,串成4颗珠子的项链,有哪些方案?</p><p><b>[解]</b>正4边形的运动群<br>绕心转 ±90<sup>。</sup> (4)<sup>1</sup> 2个<br> 180<sup>。</sup> (2)<sup>2</sup> 1个<br>绕轴翻转 (2)<sup>2</sup> 1个<br> (1)<sup>2</sup>(2) 2个<br>不动 (1)<sup>4</sup> 1个<br>P(b,g,r)=[(b+g+r)<sup>4</sup>+2(b<sup>4</sup>+g<sup>4</sup>+r<sup>4</sup>)+3(b<sup>2</sup>+g<sup>2</sup>+r<sup>2</sup>)<sup>2</sup>+2(b+g+r)<sup>2</sup>(b<sup>2</sup>+g<sup>2</sup>+r<sup>2</sup>)]/8 =b<sup>4</sup>+g<sup>4</sup>+r<sup>4</sup>+b<sup>3</sup>g+b<sup>3</sup>r+bg<sup>3</sup>+br<sup>3</sup>+g<sup>3</sup>r+gr<sup>3</sup>+2b<sup>2</sup>g<sup>2</sup>+2b<sup>2</sup>r<sup>2</sup>+2g<sup>2</sup>r<sup>2</sup>+2b<sup>2</sup>gr+2bg<sup>2</sup>r+2bgr<sup>2</sup></p><p><b>[例2]</b>4颗红色珠子嵌在正6面体的4个顶点上,有多少方案?</p><p><b>[解]</b> 相当于对顶点2着色。无珠设b。<br> (1) 1个; (4) 6个; (2) 9个; (1)(3) 8个<br>P(x,y)=[(b+r)<sup>8</sup>+6(b<sup>4</sup>+r<sup>4</sup>)<sup>2</sup>+9(b<sup>2</sup>+r<sup>2</sup>)<sup>4</sup>+8(b+r)<sup>2</sup>(b<sup>3</sup>+r<sup>3</sup>)<sup>2</sup>]/24<br>b<sup>4</sup>r<sup>4</sup>的系数:[8!/(4!·4!)+6·2+9·4!/(2!·2!)+8·2]/24=7<br><img width=434 height=219 src="./4_7/image001.gif" align="middle"></p></body></html>
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