1 + 4 + 7 + ....... + 301 = 15 251
→ stabilesc cati termeni are suma cu ratia 3 ( 4 - 1 = 3; 7 - 4 = 3;...... )
( 301 - 1 ) : 3 + 1 = 300 : 3 + 1 = 101 termeni are suma
→ aplic formula sumei lui Gauss
= 101 × ( 1 + 301 ) / 2 =
= 101 × 302 / 2 =
= 101 × 151 =
= 15 251
