a(0)=0, a(1)=1, a(n)=min{3 a(k) + 2^(n-k)-1, k=0..(n-1)} for n>=2.

Terms

a(0) =0a(1) =1a(2) =3a(3) =6a(4) =10a(5) =16a(6) =24a(7) =33a(8) =45a(9) =61a(10) =79a(11) =103a(12) =130a(13) =162a(14) =198a(15) =246a(16) =300a(17) =364a(18) =436a(19) =517a(20) =613a(21) =721a(22) =849a(23) =993a(24) =1155a(25) =1347a(26) =1563a(27) =1806a(28) =2062a(29) =2350