Bisection of A001400.

Terms

a(0) =1a(1) =3a(2) =6a(3) =11a(4) =18a(5) =27a(6) =39a(7) =54a(8) =72a(9) =94a(10) =120a(11) =150a(12) =185a(13) =225a(14) =270a(15) =321a(16) =378a(17) =441a(18) =511a(19) =588a(20) =672a(21) =764a(22) =864a(23) =972a(24) =1089a(25) =1215a(26) =1350a(27) =1495a(28) =1650a(29) =1815