Let be defined as follows:
And for every , let be the smallest non-negative integer such that:
Calculate the value of
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We will calculate Z i one by one for the required values, using the same trick to reduce the problem each time.
1 2 0 1 3 + 2 2 0 1 3 + 3 2 0 1 3 + ⋯ + 2 0 1 4 2 0 1 3 ≡ Z 2 0 1 3 ( m o d 2 0 1 3 )
Grouping terms:
( 1 2 0 1 3 + 2 0 1 2 2 0 1 3 ) + ( 2 2 0 1 3 + 2 0 1 1 2 0 1 3 ) + ⋯ + 2 0 1 3 2 0 1 3 + 2 0 1 4 2 0 1 3
Which factors as,
( 1 + 2 0 1 2 ) ( … ) + ( 2 + 2 0 1 1 ) ( … ) + ( 3 + 2 0 1 0 ) ( … ) + ⋯ + 2 0 1 3 2 0 1 3 + 2 0 1 4 2 0 1 3
Every pair is divisible by 2 0 1 3 and thus is ≡ 0 ( m o d 2 0 1 3 ) , and we are left with 2 0 1 3 2 0 1 3 + 2 0 1 4 2 0 1 3 ≡ 0 2 0 1 3 + 1 2 0 1 3 = 1 ( m o d 2 0 1 3 ) , so Z 2 0 1 3 = 1 .
The same trick reduces Z 2 0 1 4 to 1 0 0 7 2 0 1 3 + 2 0 1 4 2 0 1 3 ≡ 1 0 0 7 2 0 1 3 + 0 2 0 1 3 = 1 0 0 7 2 0 1 3 ( m o d 2 0 1 4 ) , and then we calculate 1 0 0 7 2 0 1 3 mod 2 0 1 4 .
2 ⋅ 1 0 0 7 2 0 1 3 ≡ 0 ( m o d 2 0 1 4 ) ⇒ 1 0 0 7 2 0 1 3 ≡ 0 or 1 0 0 7 ( m o d 2 0 1 4 )
Clearly, 2 0 1 4 does not divide 1 0 0 7 , so 1 0 0 7 2 0 1 3 ≡ 1 0 0 7 ( m o d 2 0 1 4 ) , and thus Z 2 0 1 4 = 1 0 0 7 .
Continuing the same ideas, we find Z 2 0 1 5 = 0 , and Z 2 0 1 6 = 1 .
2 Z 2 0 1 3 + Z 2 0 1 4 + 5 Z 2 0 1 5 − 1 0 0 Z 2 0 1 6 = 2 + 1 0 0 7 + 0 − 1 0 0 = 9 0 9