S1 =2^0+2^1+...+2^n+2^(n+1)+...+[2^(n-2)]^(n+1)=>
S1=2^0+2^1+...+2^(n-2)*(n+1)
Observi ca Termenii lui S1 reprezinta o progresi geometrica cu ratia q= 2 si (n-2)*(n+1) termeni
SCrii S1 formula sumei termenilor unei progresii geometrice
S1={[(2^(n-1)*(n+1)+1]-1}/2-1 = {[(2^(n-2)*(n+1)+1]-1}
S=1+S1