Answer:
4^n-1
Step-by-step explanation:
So given sequence is a geometric sequence where terms increase or decrease by a constant common ratio(r)
Formula to find terms in Geometric sequence is " ar^n-1 where a is first term , r is common ratio and n is number of items
In this case , first term (a) is 1 , common ratio(r) is succeeding term/preceding term = 4/1 = 4 and number of items be (n).
Applying "ar^n-1 " we get,
1*4^n-1 which is , 4^n-1
Thats the formula which represents the situation....