Bisection of A028289.

Terms

a(0) =1a(1) =2a(2) =5a(3) =11a(4) =17a(5) =27a(6) =42a(7) =57a(8) =78a(9) =106a(10) =134a(11) =170a(12) =215a(13) =260a(14) =315a(15) =381a(16) =447a(17) =525a(18) =616a(19) =707a(20) =812a(21) =932a(22) =1052a(23) =1188a(24) =1341a(25) =1494a(26) =1665a(27) =1855a(28) =2045a(29) =2255