Pascal was a French mathematician in the 1600s.
He worked with a pattern of numbers (Pascal's triangle)
to solve many counting problems.
is formed by putting 1's along two "sides" of
a triangle, then adding the two numbers above to the right
and left to get the next number in the pattern.
Pascal's triangle can be
used to solve the challenge.
Pascal's triangle was in Chu Shih-chieh's
Precious Mirror of Four Elements, a fourteenth century
book in China.