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本帖最后由 王守恩 于 2021-7-27 19:00 编辑
提醒得好!改了一下。还有错吗?我是根据11楼的资料出来的呀?
\(a(n)=\lfloor\frac{n!}{5*5!(n-5)!}\rfloor+\lfloor\frac{n}{5}\rfloor-\lfloor\frac{n}{5^2}\rfloor\)
{1, 2, 5, 12, 26, 52, 94, 160, 259, 402, 603, 876, 1240, 1716, 2328,
3104, 4073, 5270, 6733, 8504, 10630, 13160, 16150, 19660, 23755,
28506, 33987, 40280, 47472, 55656, 64932, 75404, 87185, 100394,
115157, 131608, 149886, 170140, 192526, 217208, 244359, 274158,
306795, 342468, 381384, 423760, 469820, 519800, 573945, 632510,
695761, 763972, 837430, 916432, 1001286, 1092312}
\(特别地\ \ a(500)=51048937600\) |
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