x由数码0, 5组成(个位数=5),x*x由数码0, 2, 5组成。
老规矩。我们还是想找个无限数字串。先来个引子。
1, 1表示: x=505,
2,1, 2,1表示: x=500505,
2,4,1, 2,4,1表示: x=50050000505,
3,1,4,2, 3,1,4,2表示: x=500050500005005,
4,2,6,3,1,
6,3,1,11,4,2
9,4,2,13,6,3,1,
13,6,3,1,19,9,4,2
19,9,4,2,27,13,6,3,1,
27,13,6,3,1,39,19,9,4,2
39,19,9,4,2,55,27,13,6,3,1,
55,27,13,6,3,1,79,39,19,9,4,2
79,39,19,9,4,2,111,55,27,13,6,3,1,
111,55,27,13,6,3,1,159,79,39,19,9,4,2,
......
{4, 6, 9, 13, 19, 27, 39, 55, 79, 111, 159, 223, 319, 447, 639, 895, 1279, 1791, 2559, 3583, 5119, 7167}
- Table[(6 - Cos[n*Pi])*2^Floor[n/2] - 1, {n, 0, 28}]
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还有比这更短的无限数字串?好像没有了。 |