a(n) = 2*a(n-1) - a(n-2) + a(n-3) + 2^(n-1).

Terms

a(0) =0a(1) =1a(2) =4a(3) =11a(4) =27a(5) =63a(6) =142a(7) =312a(8) =673a(9) =1432a(10) =3015a(11) =6295a(12) =13055a(13) =26926a(14) =55284a(15) =113081a(16) =230572a(17) =468883a(18) =951347a(19) =1926527a(20) =3894878a(21) =7863152a(22) =15855105a(23) =31936240a(24) =64269135a(25) =129234351a(26) =259690239a(27) =521524126a(28) =1046810092a(29) =2100221753