A049031/2.

Terms

a(0) =0a(1) =0a(2) =1a(3) =4a(4) =10a(5) =20a(6) =40a(7) =70a(8) =112a(9) =168a(10) =252a(11) =360a(12) =495a(13) =660a(14) =880a(15) =1144a(16) =1456a(17) =1820a(18) =2275a(19) =2800a(20) =3400a(21) =4080a(22) =4896a(23) =5814a(24) =6840a(25) =7980a(26) =9310a(27) =10780a(28) =12397a(29) =14168