Least number k with A309004(k) = n.

Terms

a(0) =1a(1) =12a(2) =60a(3) =420a(4) =4620a(5) =360a(6) =1021020a(7) =19399380a(8) =446185740a(9) =13860a(10) =401120980260a(11) =2520a(14) =180180a(19) =27720a(20) =3063060