I posted this challenge in the Math and Science thread, but figured I'd also post it here as this one gets checked far more often.
Challenge: Using the given values, define a function for f(x, y), then evaluate f(4, 4)
Given: f(x, y) is defined recursively
f(1, y) = f(2, y-1)
Hint: Values can easily be found by differentiating a certain trig function many times over.
f(1, 1) = 1 f(1, 2) = 2 f(1, 3) = 16
f(2, 1) = 2 f(2, 2) = 16 f(2, 3) = 272
f(3, 1) = 4 f(3, 2) = 88 f(3, 3) = 2880
f(4, 1) = 8 f(4, 2) = 416 f(4, 3) = 24576
f(5,1) = 16 f(5, 2) = 1824
f(6, 1) = 32
In 5 or 6 hours, I will post the answer.