Number of partitions of 3n in which every part is <n.

Terms

a(0) =0a(1) =1a(2) =5a(3) =19a(4) =54a(5) =141a(6) =331a(7) =733a(8) =1527a(9) =3060a(10) =5888a(11) =11004a(12) =19978a(13) =35452a(14) =61538a(15) =104875a(16) =175618a(17) =289656a(18) =470914a(19) =755880a(20) =1198693a(21) =1880246a(22) =2918919a(23) =4488553a(24) =6840398a(25) =10337947a(26) =15500575a(27) =23070000a(28) =34094908a(29) =50055877