Number of compositions of 2n into parts with multiplicity <= n.

Terms

a(0) =1a(1) =1a(2) =7a(3) =26a(4) =114a(5) =459a(6) =1892a(7) =7660a(8) =31081a(9) =125464a(10) =506025a(11) =2036706a(12) =8189555a(13) =32894825a(14) =132033140a(15) =529614616a(16) =2123365038a(17) =8509634259a(18) =34092146068a(19) =136546197412a(20) =546774790297