Question

u(a)=u(2^2015+3^2015+4^2015+5^2015)

Answer 1

U(a)=u(2^2015+3^2015+4^2015+5^2015)
2^1=2
2^2=4
2^3=8
2^4=16=u(2^4)=6
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u(2^5)=2
u(2^2015)=8

3^1=3
3^2=9
3^3=27
3^4=81
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3^5=243
3^2015=7

4^1=4
4^2=16
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4^3= 64
4^2015=6

5^1=5
-----------------
5^2=25
5^2015=5

u(2^2015+3^2015+4^2015+5^2015)=8+7+6+5= 15+11=6