1/4 + 1/16 + 1/64 + 1/256 + … = 1/3 1/3 + 1/9 + 1/27 + 1/81 + … = 1/2 1/2 + 1/4 + 1/8 + 1/16 + … = 1 1 + 2 + 3 + … + n = n * (n+1) / 2 1 + 3 + 5 + … + (2n − 1) = n2 a2 + b2 = c2 CITATION (...