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ROSECODE 454

Automatic typewriter

liuguangxi · Probability ·

An automatic typewriter can generate a random digit string by generating a sequence of random digits and concatenating them together. Each digit is chosen independently from 0 to 9 with probability 1/55, 2/55, 3/55, 4/55, 5/55, 6/55, 7/55, 8/55, 9/55 and 10/55, respectively. The generation is stopped as soon as a specific pattern occurs in the random string.

D(n) is a string consisting of first n digits of π. For example, D(3)=314, D(10)=3141592653.

Let E(n) be the expected length of the generated random string for the string pattern D(n). For example, E(3)=4159.375, E(10)=104702034619.87625.... Usually E(n) is a decimal number.

Let S(n) be E(n) rounded to the nearest integer. You are given S(3)=4159, S(10)=104702034620 and S(50)=1812330404172820790558529569081392090013172561045583.

Find S(10000).

As the answer is a very big number, use the following condensed representation:
(First 10 digits)[(number of remaining digits)](Last 10 digits)
For instance, the representation of 2127 is: 1701411834[19]5884105728.

Answer format: [condensed representation of S(10000)]

Example: 1812330404[32]2561045583 for S(50).