Răspuns:
S1=3(1+2+3+...+19)=3(19•20)/2=570
S2=9(1+2+3+...+39)=9(39•40)/2=7020
S3=5(1+2+3+...+400)=5(400•401)/2=401000
S4=4(1+2+3+...+1000)=4(1000•1001)/2=2002000
S5=8(1+2+3+...+100)=8(100•101)/2=40400
S6=11(1+2+3+...+500)=11(500•501)/2=1377750
S7=13(1+2+3+...+20)=13(20•21)/2=2730
S8=20(1+2+3+...+30)=20(30•31)/2=9300
