a(1)=1到a(8)=19反链:
{{1}} {{2}} {{3}} {{4}} {{5}} {{6}}
{{1,2}} {{1,3}} {{1,4}} {{1,5}}
{{1},{2}} {{1},{3}} {{2,3}} {{2,4}}
{{1},{4}} {{1,2,3}}
{{2},{3}} {{1},{5}}
{{2},{4}}
{{1},{2,3}}
{{2},{1,3}}
{{3},{1,2}}
{{1},{2},{3}}
.
{{7}} {{8}}
{{1,6}} {{1,7}}
{{2,5}} {{2,6}}
{{3,4}} {{3,5}}
{{1,2,4}} {{1,2,5}}
{{1},{6}} {{1,3,4}}
{{2},{5}} {{1},{7}}
{{3},{4}} {{2},{6}}
{{1},{2,4}} {{3},{5}}
{{2},{1,4}} {{1},{2,5}}
{{4},{1,2}} {{1},{3,4}}
{{1,2},{1,3}} {{2},{1,5}}
{{1},{2},{4}} {{3},{1,4}}
{{4},{1,3}}
{{5},{1,2}}
{{1,2},{1,4}}
{{1,2},{2,3}}
{{1},{2},{5}}
{{1},{3},{4}}