#3, 6, 12, 24, 48, . . .# is a geometric sequence with #3# as first term and subsequent terms being multiplied by #2#. In a geometric sequence with #a# as first term and subsequent terms being multiplied by #r#, #n^(th)# term is given by
#a*r^(n-1)# and hence #n^(th)# term of the geometric sequence is given by
#3*2^(n-1)#