First index k where A366574(k) = n.

Terms

a(0) =1a(1) =3a(2) =8a(3) =18a(4) =37a(5) =70a(6) =123a(7) =203a(8) =318a(9) =477a(10) =690a(11) =968a(12) =1323a(13) =1768a(14) =2317a(15) =2985a(16) =3788a(17) =4743a(18) =5868a(19) =7182a(20) =8705a(21) =10458a(22) =12463a(23) =14743a(24) =17322a(25) =20225a(26) =23478a(27) =27108a(28) =31143a(29) =35612