u (2017 la puterea 2017) = U(7^2017) = U(7^1) = 7
u (2018 la puterea 2018) = U(8^2018) = U(8^2) = U(64) = 4
u (2019 la puterea 2019) = U(9^2019) = 9
u (2020 la puterea 2020) = 0
________________________
cateva explicatii ptr fiecare in parte :
----- 2017 = 4 × 504 + 1
----- 2018 = 4 × 504 + 2
----- 9 la o putere para are ultima cifra 1
----- 9 la o putere impara (2019) are ultima cifra 9
----- un numar care se termina in 0, la orice putere va avea ultima cifra 0 .
