Find the law, 1 / 2, 1 / 3, 1 / 10, 1 / 15, 1 / 26. The ninth number is Fast

The numerator is invariable, and the denominator is as follows
2 = the square of 1 + 1
3 = 2 squared-1
10 = the square of 3 + 1
15 = square of 4-1
26 = the square of 5 + 1
.
In this order, the ninth number is:
Square of 9 + 1 = 82
That's 1 / 82