For integer , find the number of such that the infinitely nested fraction above is an integer.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Let the nested fraction =y
Then y = 2 + y x − 1
y 2 + 2 y = x − 1
y 2 + 2 y + 1 = x
( y + 1 ) 2 = x
Since ( y + 1 ) 2 is an integer, x must be a square number.
The question now is, how many natural numbers up to 2015 are square numbers?
2 0 1 5 ≈ 4 4 . 8 9
Rounding down, we get the answer,
4 4