Salut! :)
A = 3⁰ + 3¹ + 3² + ... + 3⁴⁴
A = ( 3⁰ + 3¹ + 3² ) + ( 3³ + 3⁴ + 3⁵ ) + ... + ( 3⁴² + 3⁴³ + 3⁴⁴ )
A = 3⁰ × ( 1 + 3 + 3² ) + 3³ × ( 1 + 3 + 3² ) + ... + 3⁴² × ( 1 + 3 + 3² )
A = 3⁰ × 13 + 3³ × 13 + ... + 3⁴² × 13
A = 13 × ( 3⁰ + 3³ + ... + 3⁴² ) ➺ A este divizibil cu 13