a(n)=n for n <= 3, a(n) = 2a(n-1) - 2a(n-2) + 2a(n-3) for n >= 4.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =6a(6) =10a(7) =16a(8) =24a(9) =36a(10) =56a(11) =88a(12) =136a(13) =208a(14) =320a(15) =496a(16) =768a(17) =1184a(18) =1824a(19) =2816a(20) =4352a(21) =6720a(22) =10368a(23) =16000a(24) =24704a(25) =38144a(26) =58880a(27) =90880a(28) =140288a(29) =216576