For the given series reaction in nth step, find out the number of produced neutrons and energy-
238U→Ba+Kr+3n+Energy(E)

Every step releases three neutrons during this decay series.
And it is a chain reaction in which every neutron is going to create a new step to generate 3 more neutrons
It means up to nth step 3ⁿ  neutrons are released
Energy for the first step is E .hence E is 3^n-1 E