a(3)=64连通连通系统:
{{123}} {{1}{123}}
{{12}{123}} {{2}{123}}
{{13}{123}} {{3}{123}}
{{23}{123}} {{1}{12}{123}}
{{12}{13}{123}} {{1}{13}{123}}
{{12}{23}{123}} {{1}{23}{123}}
{{13}{23}{123}} {{2}{12}{123}}
{{12}{13}{23}{123}} {{2}{13}{123}}
{{2}{23}{123}}
{{3}{12}{123}}
{{3}{13}{123}}
{{3}{23}{123}}
{{1}{12}{13}{123}}
{{1}{12}{23}{123}}
{{1}{13}{23}{123}}
{{2}{12}{13}{123}}
{{2}{12}{23}{123}}
{{2}{13}{23}{123}}
{{3}{12}{13}{123}}
{{3}{12}{23}{123}}
{{3}{13}{23}{123}}
{{1}{12}{13}{23}{123}}
{{2}{12}{13}{23}{123}}
{{3}{12}{13}{23}{123}}
.
{{1}{2}{123}} {{1}{2}{3}{123}}
{{1}{3}{123}} {{1}{2}{3}{12}{123}}
{{2}{3}{123}} {{1}{2}{3}{13}{123}}
{{1}{2}{12}{123}} {{1}{2}{3}{23}{123}}
{{1}{2}{13}{123}} {{1}{2}{3}{12}{13}{123}}
{{1}{2}{23}{123}} {{1}{2}{3}{12}{23}{123}}
{{1}{3}{12}{123}} {{1}{2}{3}{13}{23}{123}}
{{1}{3}{13}{123}} {{1}{2}{3}{12}{13}{23}{123}}
{{1}{3}{23}{123}}
{{2}{3}{12}{123}}
{{2}{3}{13}{123}}
{{2}{3}{23}{123}}
{{1}{2}{12}{13}{123}}
{{1}{2}{12}{23}{123}}
{{1}{2}{13}{23}{123}}
{{1}{3}{12}{13}{123}}
{{1}{3}{12}{23}{123}}
{{1}{3}{13}{23}{123}}
{{2}{3}{12}{13}{123}}
{{2}{3}{12}{23}{123}}
{{2}{3}{13}{23}{123}}
{{1}{2}{12}{13}{23}{123}}
{{1}{3}{12}{13}{23}{123}}
{{2}{3}{12}{13}{23}{123}}