Number of set partitions of [n] into three blocks with distinct sizes.

Terms

a(0) =60a(1) =105a(2) =448a(3) =2016a(4) =4980a(5) =15675a(6) =61644a(7) =155155a(8) =482573a(9) =1733550a(10) =4549808a(11) =13890360a(12) =48104628a(13) =128949675a(14) =392009140a(15) =1322692581a(16) =3607864403a(17) =10929721440a(18) =36245555284a(19) =100109572875a(20) =302709337515a(21) =990788537700