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例子
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集合s={3,4,6,8,9}将分区{3,6,8,9}和{3,8},{6,9}}的块数相等,因此s在a(9)下计数。
a(3)=1到a(6)=19个子集:
{1,2,3} {1,2,3} {1,2,3} {1,2,3}
{1,3,4} {1,3,4} {1,3,4}
{1,2,3,4} {1,4,5} {1,4,5}
{2,3,5} {1,5,6}
{1,2,3,4} {2,3,5}
{1,2,4,5} {2,4,6}
{2,3,4,5} {1,2,3,4}
{1,2,3,4,5} {1,2,3,6}
{1,2,4,5}
{1,2,5,6}
{1,3,4,6}
{2,3,4,5}
{2,3,5,6}
{3,4,5,6}
{1,2,3,4,5}
{1,2,3,4,6}
{1,2,4,5,6}
{2,3,4,5,6}
{1,2,3,4,5,6}
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