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Level 2

Compute the remainder when N N is divided by 19 19 .

N = n = 1 2014 n 2014 \large{N=\sum_{n~=~1}^{2014}~n^{2014}}


The answer is 0.

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2 solutions

Jubayer Nirjhor
Jan 3, 2014

Note that: n = 1 18 n 2014 = ( 1 2014 + + 8 2014 + 9 2014 ) + ( 1 0 2014 + + 1 8 2014 ) = ( n = 1 9 n 2014 ) + ( n = 10 18 n 2014 ) = ( n = 1 9 n 2014 ) + ( n = 10 18 n 2013 n ) ( n = 1 9 n 2014 ) + ( n = 1 9 ( n ) 2013 n ) ( m o d 19 ) = ( n = 1 9 n 2014 ) + ( n = 1 9 n 2014 ) = ( n = 1 9 n 2014 ) ( n = 1 9 n 2014 ) = 0 \begin{aligned} \text{Note that:}~~~ \sum_{n=1}^{18} n^{2014} &= &\left(1^{2014}+\cdot\cdot\cdot+8^{2014}+9^{2014}\right)+\left(10^{2014}+\cdot\cdot\cdot+18^{2014}\right) \\ \\ &=&\left(\sum_{n=1}^{9} n^{2014}\right) + \left(\sum_{n=10}^{18} n^{2014}\right) \\ \\ &=&\left(\sum_{n=1}^{9} n^{2014}\right) + \left(\sum_{n=10}^{18} n^{2013}\cdot n\right) \\ \\ &\equiv &\left(\sum_{n=1}^{9} n^{2014}\right) + \left(\sum_{n=1}^{9} \left(-n\right)^{2013}\cdot n\right) \pmod{19} \\ \\ &=& \left(\sum_{n=1}^{9} n^{2014}\right) + \left(\sum_{n=1}^{9} -n^{2014}\right) \\ \\ &=& \left(\sum_{n=1}^{9} n^{2014}\right) - \left(\sum_{n=1}^{9} n^{2014}\right) \\ \\ &=& ~~~ 0 \\ \\ \end{aligned}

Therefore: n = 1 2014 n 2014 106 ( n = 1 18 n 2014 ) 106 × 0 = 0 ( m o d 19 ) \text{Therefore:}~~~ \sum_{n=1}^{2014} n^{2014} \equiv 106\cdot \left(\sum_{n=1}^{18} n^{2014}\right) \equiv 106\times 0 = \fbox{0}\pmod{19}

Masba Islam
May 4, 2014

Python Code:

s=0

for i in range(2014):

a=i+1

for j in range(2014):

    a=(a*(i+1))%19

s=s+a

print s%19

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