a(n) = floor(n*3^(n/2)).

Terms

a(0) =1a(1) =6a(2) =15a(3) =36a(4) =77a(5) =162a(6) =327a(7) =648a(8) =1262a(9) =2430a(10) =4629a(11) =8748a(12) =16414a(13) =30618a(14) =56819a(15) =104976a(16) =193187a(17) =354294a(18) =647747a(19) =1180980a(20) =2147793a(21) =3897234a(22) =7057034a(23) =12754584a(24) =23012070a(25) =41452398a(26) =74559107a(27) =133923132a(28) =240246014a(29) =430467210