Number of semistandard rectangular plane partitions of n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =9a(6) =15a(7) =20a(8) =30a(9) =42a(10) =59a(11) =79a(12) =112a(13) =146a(14) =199a(15) =264a(16) =350a(17) =455a(18) =603a(19) =774a(20) =1010a(21) =1297a(22) =1668a(23) =2124a(24) =2724a(25) =3441a(26) =4372a(27) =5513a(28) =6955a(29) =8718