4-untouchable numbers.

Terms

a(0) =298a(1) =1006a(2) =1016a(3) =1108a(4) =1204a(5) =1492a(6) =1502a(7) =1940a(8) =2164a(9) =2344a(10) =2370a(11) =2770a(12) =3116a(13) =3358a(14) =3410a(15) =3482a(16) =3596a(17) =3676a(18) =3688a(19) =3976a(20) =4076a(21) =4164a(22) =4354a(23) =4870a(24) =5206a(25) =5634a(26) =5770a(27) =6104a(28) =6206a(29) =6332