Duplicate of A077827.

Terms

a(0) =1a(1) =3a(2) =9a(3) =27a(4) =79a(5) =231a(6) =675a(7) =1971a(8) =5755a(9) =16803a(10) =49059a(11) =143235a(12) =418195a(13) =1220979a(14) =3564819