Bisection of A048654.

Terms

a(0) =4a(1) =22a(2) =128a(3) =746a(4) =4348a(5) =25342a(6) =147704a(7) =860882a(8) =5017588a(9) =29244646a(10) =170450288a(11) =993457082a(12) =5790292204a(13) =33748296142a(14) =196699484648