将点标记为1、2、3、,。..
a(2)=3:1<2,2<1,1=2。
a(3)=13来自13个排列:1<2<3,1<3<2,2<1<3,2<3<1,3<1<2,3<2<1,1=2<3 1=3<2,2=3<1,1<2=3,2<1=3,3<1=2,1=2=3。
三名选手可以以13种方式完成比赛:1、2、3; 1,3,2; 2,1,3; 2,3,1; 3,1,2; 3,2,1; 1,1,3; 2,2,1; 1,3,1; 2,1,2; 3,1,1; 1,2,2; 1,1,1.
a(3)=13。3个顶点上的13个平面增加的0-1-2树,其中出度1的顶点有3种颜色,出度2的顶点有2种颜色,如下所示:
........................................................
…….1(x3色)。….1(x2色)。…1(x2色)。。
........|................/.\............./.\............
……..2(x3色)。..2...3...........3...2...........
........|...............................................
........3...............................................
......====..............====............====............
.总计9……+。.........2....+..........2....=..13....
........................................................
a(4)=75。4个顶点上75个非平面增加的0-1-2树,其中伸出度1的顶点有3种颜色,伸出度2的顶点有4种颜色,如下所示:
...............................................................
…..1(x3)个。….1(x4)。……1(x4)。….1(x4)。…….1(x3)。......
.....|........./.\........./.\......./.\...........|...........
…..2(x3)个。..2…3.(x3)。.3…2(x3).4…2(x 3)。…..2(x4)。......
.....|.............\...........\.........\......../.\..........
…..3.(x3)。........4...........4.........3......3...4.........
.....|.........................................................
.....4.........................................................
....====......=====........====......====.........====.........
总计27….+。...12......+...12....+...12.......+...12...=...75.
字母表{1,2,3}上的a(3)=13个字符串包含所有出现最大值的字母,相应的有序集分区为:
01: [ 1 1 1 ] { 1, 2, 3 }
02: [ 1 1 2 ] { 1, 2 } < { 3 }
03: [ 1 2 1 ] { 1, 3 } < { 2 }
04: [ 2 1 1 ] { 2, 3 } < { 1 }
05: [ 1 2 2 ] { 1 } < { 2, 3 }
06: [ 2 1 2 ] { 2 } < { 1, 3 }
07: [ 2 2 1 ] { 3 } < { 1, 2 }
08: [ 1 2 3 ] { 1 } < { 2 } < { 3 }
09: [ 1 3 2 ] { 1 } < { 3 } < { 2 }
00: [ 2 1 3 ] { 2 } < { 1 } < { 3 }
11: [ 2 3 1 ] { 3 } < { 1 } < { 2 }
12: [ 3 1 2 ] { 2 } < { 3 } < { 1 }
13: [ 3 2 1 ] { 3 } < { 2 } < { 1 }
(结束)