Number of shifted Young tableaux with height <= 3.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =12a(6) =27a(7) =63a(8) =154a(9) =386a(10) =989a(11) =2574a(12) =6787a(13) =18085a(14) =48622a(15) =131719a(16) =359194a(17) =985186a(18) =2715973a(19) =7521568a(20) =20915257a(21) =58373587a(22) =163462816a(23) =459136810a(24) =1293223231a(25) =3651864607a(26) =10336625732a(27) =29321683083a(28) =83344398534a(29) =237344961292