A transform of C(n,2).

Terms

a(0) =0a(1) =0a(2) =1a(3) =6a(4) =30a(5) =140a(6) =615a(7) =2562a(8) =10220a(9) =39384a(10) =147645a(11) =541310a(12) =1948650a(13) =6908772a(14) =24180611a(15) =83702010a(16) =286978200a(17) =975725744a(18) =3293074233a(19) =11041484022a(20) =36804946550a(21) =122037454140a(22) =402723598431