Triangle of unsigned 2-Lah numbers.

Terms

a(0) =1a(1) =4a(2) =1a(3) =20a(4) =10a(5) =1a(6) =120a(7) =90a(8) =18a(9) =1a(10) =840a(11) =840a(12) =252a(13) =28a(14) =1a(15) =6720a(16) =8400a(17) =3360a(18) =560a(19) =40a(20) =1a(21) =60480a(22) =90720a(23) =45360a(24) =10080a(25) =1080a(26) =54a(27) =1a(28) =604800a(29) =1058400