Enumeration of | Sort_n(123,321) |.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =7a(5) =14a(6) =28a(7) =56a(8) =112a(9) =224a(10) =448a(11) =896a(12) =1792a(13) =3584a(14) =7168a(15) =14336a(16) =28672a(17) =57344a(18) =114688a(19) =229376a(20) =458752a(21) =917504a(22) =1835008a(23) =3670016a(24) =7340032a(25) =14680064a(26) =29360128a(27) =58720256a(28) =117440512a(29) =234881024