[tex]u(16^{2006}+17^{2007}+18^{2008}+19^{2009}+20^{2010})= \\
u[u(6^{2006})+u(7^{2007})+u(8^{2008})+u(9^{2009})+u(0^{2006})]= \\
u(6^{2006})=6~pt.~ca:\\
u(6^1)=6;~u(6^2)=6;~u(6^3)=6 \\
u(7^{2007})=3~pt.~ca:\\
2007:4=501~r~3;~u(7^3)=3 \\
u(8^{2008})= 0~pt.~ca:\\
2008:4=502~r~0;~u(7^0)=1 \\
u(9^{2009})=9~pt.ca:\\
2009:4=502~r~1;~u(9^1)=9 \\
u(0^{2006})=0 \\
u(6+3+1+9+0)=u(19)=9[/tex]
