Number of admissible sequences of order j; related to 5x+1 problem.

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =56a(5) =202a(6) =715a(7) =3244a(8) =12945a(9) =49742a(10) =238048a(11) =996158a(12) =3991995a(13) =19676358a(14) =84649176a(15) =347993910a(16) =1747681160a(17) =7656026268a(18) =32018897274a(19) =162900330572a(20) =722787262419