Number of branches in all hex trees with n edges (n>=1).

Terms

a(0) =3a(1) =11a(2) =48a(3) =224a(4) =1071a(5) =5169a(6) =25053a(7) =121711a(8) =592233a(9) =2885397a(10) =14073318a(11) =68710266a(12) =335775825a(13) =1642305765a(14) =8039194560a(15) =39382567940a(16) =193067419905a(17) =947129136345