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Puzzles

17 December

A sequence of zeros and ones can be reduced by writing a 0 or 1 under each pair of numbers: 1 is written if the numbers are the same, 0 is written if they are not. This process can be repeated until there is a single number. For example, if we start with the sequence 1, 1, 1, 0, 1 (of length 5), we get:
1
1
1
0
1
1
1
0
0
1
0
1
0
0
1
The final digit is a 1.
How many sequences of zeros and ones of length 10 are there that when reduced lead to the final digit being a 1?

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24 December

When written in binary, the number 235 is 11101011. This binary representation starts and ends with 1 and does not contain two 0s in a row.
What is the smallest three-digit number whose binary representation starts and ends with 1 and does not contain two 0s in a row?

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