help me answer this!

Question

chess board has one grain of wheat on the First Square, two grains on the second square, four grains on the third square, eight grains on the fourth square, and so on, up to and including the 18th square. Find the total number of grains on the board.

Answer 1

A chess board has 64 squares

S_n = a₁(rⁿ - 1) / (r - 1)

S_n = 1(2⁶⁴ - 1) / (2 - 1)

S_n = 1(68719476740 - 1)

S_n = 18,446,744,073,709,551,616 - 1