explicit formula

Question

6,30,150,750

 

answer boxes are 

 

a=___  times with the dot (___)^n-1,for n_>__1

  n

Answer 1

See if you can figure out the common ratio r between successive terms, and the first term a₁.  Then use the formula for a geometric sequence that  

 

a_n = a₁r^(n-1)