证明了有限偏序集的几个重要结果,利用这些结果并借助于拓扑空间对应的特殊化序与拓扑之间的关系计算得出4元素集合上T0拓扑总数为219,拓扑总数为355.
Several important results for finite posets are proved. With these results and the specialization order of a topology, as well as relationships between topologies and orderings, the total numbers of T0-topologies and of topologies on a 4-element set are calculated to be 219 and 355.