Linear Congruential Generator 1,4,9

[mebigp]

Homework Statement

X=(aX + b) mod 65536
Output is 1,4,9, ?

Can anyone give me a hint as to what a and b are

Homework Equations

The Attempt at a Solution

1=(aX + b) mod 65536
4=(a1 + b) mod 65536
9=(a4 + b) mod 65536

The values I have tried get me from 4 to 7 not 9

 

[mebigp]

By sub 5=3a mod 65536 but I am stuck here