a: =proc(n)选项记忆`如果`(n<4,[1,1,2,5][n+1],
((12*(n-1))*(182*n^3-1659*n^2+4628*n-3756)*a(n-1
-(4*(91*n^4-1057*n^3+3812*n^2-4046*n-906))*a(n-2)
+(6*(n-4))*(182*n^3-1659*n^2+4901*n-4630)*a(n-3)
-(4*(n-4))*(n-5)*(91*n^2-511*n+690)*a(n-4))
/(5*n*(n-1)*(91*n^2-693*n+1292))
结束时间: