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last digit 2^1+3^5+4^9+5^{13}+ ... +505^{2013}+506^{2017} (HOMC 2017 J Q4)

Source:

August 7, 2019

number theorylastDigit

Problem Statement

Put

S = 2^1 + 3^5 + 4^9 + 5^{13} + ... + 505^{2013} + 506^{2017}

. The last digit of

S

is
(A):

1

(B):

3

(C):

5

(D):

7

(E): None of the above.