a(n) = coefficient of 2^(2/3) in the expansion of (2^(1/3) + 2^(2/3))^n.

Terms

a(0) =0a(1) =1a(2) =1a(3) =6a(4) =12a(5) =42a(6) =108a(7) =324a(8) =900a(9) =2592a(10) =7344a(11) =20952a(12) =59616a(13) =169776a(14) =483408a(15) =1376352a(16) =3919104a(17) =11158560a(18) =31772736a(19) =90465984a(20) =257587776a(21) =733432320a(22) =2088322560a(23) =5946120576a(24) =16930529280a(25) =48206658816a(26) =137259899136a(27) =390823128576