a(0)=1, a(1)=1, a(2)=1, a(n) = 2*a(n-1) + a(n-2) + 1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =10a(5) =25a(6) =61a(7) =148a(8) =358a(9) =865a(10) =2089a(11) =5044a(12) =12178a(13) =29401a(14) =70981a(15) =171364a(16) =413710a(17) =998785a(18) =2411281a(19) =5821348a(20) =14053978a(21) =33929305a(22) =81912589a(23) =197754484a(24) =477421558a(25) =1152597601a(26) =2782616761a(27) =6717831124a(28) =16218279010a(29) =39154389145