a(0) = 0, a(1) = 1 and a(n) = 6*a(n-1)/(n-1) + 4*a(n-2) for n > 1.

Terms

a(0) =0a(1) =1a(2) =6a(3) =22a(4) =68a(5) =190a(6) =500a(7) =1260a(8) =3080a(9) =7350a(10) =17220a(11) =39732a(12) =90552a(13) =204204a(14) =456456a(15) =1012440a(16) =2230800a(17) =4886310a(18) =10647780a(19) =23094500a(20) =49884120a(21) =107343236a(22) =230205976a(23) =492156392a(24) =1049212528a(25) =2230928700a(26) =4732273000a(27) =10015777800a(28) =21154820400a(29) =44596287000