Why are we adding the no of ways in the problem

#1

f(n) = f(n-1) + f(n-4)

#2

@shiva57reddy because we have to find the total number of ways of tilling.
We have to find a recursive relation to tile a floor of size 4 x N given tile size is 1 x 4
When you keep the tile vertically, number of ways of tiling the remaining floor is f(n-1) as n-1 is the remaining width.
When you keep the tiles horizontally, number of ways of tiling remaining floor is f(n-4).
So total number of ways pf tiling is the sum of both.

#3

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