1 1 1 1 1nnR1 1 .
1 1 1 1
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... 11 1 1 .
1 1.
() () .
Although the number 1 used to be considered a prime number, it requires special treatment in so many definitions and applications involving primes greater than or equal to 2 that it is.
11 1.
11 11 111 1.
62332 161231123 1.
