a(n) = 3*A132357(n).

Terms

a(0) =3a(1) =12a(2) =42a(3) =123a(4) =366a(5) =1092a(6) =3279a(7) =9840a(8) =29526a(9) =88575a(10) =265722a(11) =797160a(12) =2391483a(13) =7174452a(14) =21523362a(15) =64570083a(16) =193710246a(17) =581130732a(18) =1743392199a(19) =5230176600a(20) =15690529806a(21) =47071589415a(22) =141214768242a(23) =423644304720