7 + 9 + 11 + ...... + 2 013 = 1 014 040
→ stabilesc cati termeni are suma cu ratia 2
( 2 013 - 7 ) : 2 + 1 = 2006 : 2 + 1 = 1003 + 1 = 1004 termeni
→ aplic formula sumei lui Gauss
= 1 004 × ( 7 + 2 013 ) / 2 =
= 502 × 2 020 =
= 1 014 040
