Number 3 can be expressed by using 1 and 2 in 3 distinct ways I,e, 1+1+1, 1+2, 2+1; number 4 in 5 ways: 1+1+1+1 , 2+1+1, 1+2+1, 1+1+2, and 2+2.

Using the digits 1 and 2 as summands, in how many ways may be 26 expressed?

Bonus: Generalize the process for number N.