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Let F5(n) be the number of strings s such that:
s consists only of '0's and '1's,
s has length at most n, and
s contains a palindromic substring of length at least 5.
For example, F5(4) = 0, F5(5) = 8, 
F5(6) = 42 and F5(11) = 3844.
Let D(L) be the number of integers n such that 
5 ≤ n ≤ L and F5(n) is divisible by 87654321.
For example, D(107) = 0 and D(5·109) = 51.
Find D(1018).

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