A dec-string is a sequence of characters from the 10-character alphabet {0,1,2,3,4,5,6,7,8,9}. For example, these are dec-strings:

0 36562342320 49548362729 

Let n0 be an integer.

1. What is the number of dec-strings d1,,dn of lenght n such that d1d2=00 or d1d2d3=111?

2. What is the number of dec-strings d1,,dn of length n4 such that d1d200 or d3d411.