How to implement recursive neural networks in Tensorflow?

I am trying to implement a very basic recursive neural network
into my linear regression analysis project in Tensorflow that takes
two inputs passed to it and then a third value of what it
previously calculated. So, my project is trying to calculate
something across the next x number of years, and after the first
year I want it to keep taking the value of the last year.
Currently, my training data has two inputs, not three, predicting
one output, so how could I make it recursive, so it keeps on
passing in the value from the last year, to calculate the next? To
explain slightly further, if it were to calculate across the next 5
years:

1st year:

Input 1: 10

Input 2: 20

(Maybe need input 3, but a value that has no affect on the
linear regression model)

Output: 30

2nd year:

Input 1: 11

Input 2: 22

Input 3: 30 (1st year output)

Output: 35

3rd Year:

Input 1:12

Input 2: 24

Input 3: 35 (2nd year output)

Output: 40