2n 2 6n 4 July 8, 2019 16 32 64 128 2n 8 2 6n 4 2n 2 4n 6n 2 2n 4 )( n 2 6n 4 2 6n 4 2n is always divisible by 6n 2 4 2n 2 9 2 + 4 + 6 + ... + 2n