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Bounded Sequences
Problem 319
Published on 08 January 2011 at 07:00 pm [Server Time]
Let x1, x2,..., xn be a sequence of length n such that:
- x1 = 2
- for all 1 < i ≤ n : xi-1 < xi
- for all i and j with 1 ≤ i, j ≤ n : (xi) j < (xj + 1)i
There are only five such sequences of length 2, namely:
{2,4}, {2,5}, {2,6}, {2,7} and {2,8}.
There are 293 such sequences of length 5; three examples are given below:
{2,5,11,25,55}, {2,6,14,36,88}, {2,8,22,64,181}.
Let t(n) denote the number of such sequences of length n.
You are given that t(10) = 86195 and t(20) = 5227991891.
Find t(1010) and give your answer modulo 109.
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