Mulcrone formulation

To avoid any numerical precision problems that may arise with the Mulcrone formulation, R. Biyani has suggested a formulation involving only integer calculations. In particular, we can use a recursive function that computes the sex, s, of the xth person in the yth year using a previously generated sequence of the number of persons taken in each year (the Fibonacci sequence). The recursive relationship is ... 

Can you use this fact to write a program to compute the sex of the billionth individual without resorting to the Mulcrone formulation ... 

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