# An unambiguous number puzzle

One is four, two is six

Three is one, four is one

Five is nine, six is five

Seven is nine, eight is nine

Nine is two, ten is five

Eleven is seven, twelve is eight.

What is thirteen?

Note: the format of this puzzle (two pairs per line) has nothing to do with the answer. Also, the numbers and their pairs follow the same rule, but are independent of each other. For example, I could accurately put "forty-one is five" in the list and it would not change any other pairs or their placement or anything.

I made sure to put enough pairs that an incorrect rule will not work or will be extremely far-fetched - hence the title.

Hint:

This puzzle should be easy. How easy? Well, as easy as (wait for it..) pi!

13 is 2

Because

n is m where m is the decimal digit following the first occurrence of the decimal digit(s) n in pi.

Like so:

3.14...

3.1415926...

3.1...

3.141...

3.14159...

3.14159265...

3.14159265358979...

3.141592653589...

3.141592...

3.141592653589793238462643383279502884197169399375105...

3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117...

3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067982148086513282306647093844609550582231725359408128...

3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132...