| 数据
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1, 1, 3, 12, 63, 403, 2919, 22833, 187799, 1599718, 13984383, 124717327, 1130144932, 10375309228, 96290993853, 901915801437, 8514822062757, 80939662475426,774025387921462,7441380898249458,71879194326339456,697253570563306939,6789448668631285664,66340474776507262638
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| 公式
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a(n))=总和() =总和_{m=1…n,总和(}总和_{k=平均值,}二项式(n-1,k-1)*m/(3*k-2*m)*binominal(4*k-3*m-1,k-m))),),n> 0,a(0)=1。
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