U15是个8阶Abel群，G=U15={1,2,4,7,8,11,13,14},元素阶为1,4,2,4,4,2,4,2,因为G有3个2阶元，所以G有直和分解G=Z4×Z2=<2>×<11>,G有六个循环子群
H1={1}
H2=<4>={1,4}
H3=<11>={1,11}
H4=<14>={1,14}
H5=<2>={1,2,4,8}
H6=<7>={1,7,4,8,13}