what is the sequence between 7, 21, 8, 72, 9

Question

what is next sequence number

 

Answer 1

7, 21, 8, 72, 9

a₁=7

a₂=3*a₁=21

a₃=1+a₁=8

a₄=3²*a₃=72

a₅=2+a₁=9

a₆=3³*a₅=3*81=243

a₇=3+a₁=10

 

a_2n-1=n+6

a_2n=(6+n)3ⁿ