That look like an obvious decreasing trend. From the first and last point we get a slope of (9-31)/(92-26) = -1/3 and a y intercept of 31 - (-1/3)26 = 39.67.
The formula for C(n,r), also known as "n choose r" or a combination, is: nCr = n! / (r!(n-r)!), where n is the total number of options and r is number you must choose
The number generated is the total number of possible combinations.
The ! means factorial. For example, 4! = 4 x 3 x 2 x 1
