Triangle read by rows. T(n,k) = binomial(n,k)*(binomial(n,k)-1)/2.

Terms

a(0) =1a(1) =3a(2) =3a(3) =6a(4) =15a(5) =6a(6) =10a(7) =45a(8) =45a(9) =10a(10) =15a(11) =105a(12) =190a(13) =105a(14) =15a(15) =21a(16) =210a(17) =595a(18) =595a(19) =210a(20) =21a(21) =28a(22) =378a(23) =1540a(24) =2415a(25) =1540a(26) =378a(27) =28a(28) =36a(29) =630