a(n) = A289676(3*n).

Terms

a(0) =1a(1) =1a(2) =3a(3) =3a(4) =12a(5) =20a(6) =39a(7) =64a(8) =116a(9) =210a(10) =438a(11) =966a(12) =2089a(13) =4155a(14) =8032a(15) =15657a(16) =30325a(17) =58379a(18) =112885