A bisection of A000960.

Terms

a(0) =1a(1) =7a(2) =19a(3) =39a(4) =63a(5) =91a(6) =133a(7) =181a(8) =223a(9) =289a(10) =349a(11) =399a(12) =481a(13) =567a(14) =649a(15) =763a(16) =843a(17) =949a(18) =1093a(19) =1189a(20) =1321a(21) =1471a(22) =1579a(23) =1719a(24) =1899a(25) =2023a(26) =2187a(27) =2367a(28) =2533a(29) =2739