The trend of huge number (4)

1 2017 2017 2017 + 2 2017 2017 2017 + 3 2017 2017 2017 + + 201 6 2017 2017 2017 \large 1^{{2017}^{{2017}^{{2017}}}}+2^{{2017}^{{2017}^{2017}}}+3^{{2017}^{{2017}^{2017}}}+\cdots+2016^{{2017}^{{2017}^{2017}}}

Find the remainder when the expression above is divided by 2017.

2015 2016 1 0 1008 2

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2 solutions

Let 201 7 201 7 2017 = n . Then: 1 n + 2 n + 3 n + + 201 6 n ( m o d 2017 ) ( 1 n + 201 6 n ) + ( 2 n + 201 5 n ) + ( 3 n + 201 4 n ) + + ( 100 8 n + 100 9 n ) ( m o d 2017 ) ( 1 n + ( 1 ) n ) + ( 2 n + ( 2 ) n ) + ( 3 n + ( 3 ) n ) + + ( 1008 n + ( 1008 ) n ) ( m o d 2017 ) n is odd,so: ( a ) n = a n a n + ( a ) n = 0 j = 1 1008 ( j n + ( j ) n ) = j = 1 1008 0 = 0 \text{Let}\; 2017^{2017^{2017}}=n.\text{Then:}\\ 1^n+2^n+3^n+\cdots +2016^n\pmod{2017}\\ (1^n+2016^n)+(2^n+2015^n)+(3^n+2014^n)+\cdots+(1008^n+1009^n)\pmod{2017}\\ (\color{#3D99F6}{1}^n+\color{#3D99F6}{(-1)}^n)+(\color{#3D99F6}{2}^n+\color{#3D99F6}{(-2)}^n)+(\color{#3D99F6}{3}^n+\color{#3D99F6}{(-3)}^n)+\cdots+(\color{#3D99F6}{1008}^n+\color{#3D99F6}{(-1008)}^n)\pmod{2017}\\ n\;\text{is odd,so:}\\ (-a)^n=-a^n\implies \boxed{a^n+(-a)^n=0}\\ \implies \sum^{1008}_{j=1} (\color{teal}{j^n+(-j)^n})=\sum^{1008}_{j=1} \color{#D61F06}{0}=\color{#20A900}{\boxed{\boxed{0}}}

Tommy Li
Jul 4, 2016

Relevant wiki: Fermat's Little Theorem

1 2017 2017 2017 + 2 2017 2017 2017 + 3 2017 2017 2017 + + 201 6 2017 2017 2017 x ( m o d 2017 ) \large 1^{{2017}^{{2017}^{{2017}}}}+2^{{2017}^{{2017}^{2017}}}+3^{{2017}^{{2017}^{2017}}}+\dots+2016^{{2017}^{{2017}^{2017}}} \equiv x \pmod{2017}

1 + 2 + 3 + + 2016 x ( m o d 2017 ) \large 1+2+3+\dots+2016 \equiv x \pmod{2017} (By Fermat's little theorem)

( 2016 ) ( 2016 + 1 ) 2 x ( m o d 2017 ) \large \frac{(2016)(2016+1)}{2} \equiv x \pmod{2017}

( 1008 ) ( 2017 ) x ( m o d 2017 ) \large (1008)(2017) \equiv x \pmod{2017}

x 0 ( m o d 2017 ) \large x \equiv 0 \pmod{2017}

You must know 2017 is prime first.

Jaleb Jay - 4 years, 11 months ago

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