Why do you multiply by 4 and 6?

[consideratewallaby 0]

I understood everything until the part which said (1 + 2 + 2² + 2³) × 4 × 6. Where did the 4 and the 6 come from?

[daringhorse]

You multiply (2^0 x 2^1 x 2^2 x 2^3) with (3^0 x 3^1)=4
and you also multiply that with (5^0 x 5^1)= 6

[Meth]

@daringhorse i think you meant 3^0+3^1 and 5^0+5^1 right, i just want to check