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Problem 225


Problem 225


Tribonacci non-divisors

The sequence 1, 1, 1, 3, 5, 9, 17, 31, 57, 105, 193, 355, 653, 1201 …
is defined by T1 = T2 = T3 = 1 and Tn = Tn-1 + Tn-2 + Tn-3.

It can be shown that 27 does not divide any terms of this sequence. In fact, 27 is the first odd number with this property.

Find the 124th odd number that does not divide any terms of the above sequence.


三阶斐波那契数的非约数

序列1, 1, 1, 3, 5, 9, 17, 31, 57, 105, 193, 355, 653, 1201 …
的定义为T1 = T2 = T3 = 1以及Tn = Tn-1 + Tn-2 + Tn-3

可以说明,27不能整除这个序列中的任何一项。事实上,27是第一个拥有这一性质的奇数。

求第124个不能整除上述序列中任何一项的奇数。