1 + 4 + 7 + 10 + ... + 196 + 199 =
= 3×0+1 + 3×1+1 + 3×2+1 + 3×3+1 + ... + 3×65+1 + 3 × 66 + 1 =
= 3 × (0 + 1 + 2 + 3 + ...+ 66) + 1+1+1+...+1 de 67 ori =
= 3 × 66 × 67 : 2 + 1 × 67 =
= 3×33 × 67 + 67 =
= 67 × (99 + 1) =
= 67 × 100 =
= 6 700 (suma tuturor numerelor sterse de pe tabla, mai mici decat 200)