Smallest number requiring n chisel strokes for its representation in Roman numerals.

Terms

a(0) =1a(1) =2a(2) =3a(3) =7a(4) =8a(5) =17a(6) =18a(7) =27a(8) =28a(9) =37a(10) =38a(11) =87a(12) =88a(13) =187a(14) =188a(15) =287a(16) =288a(17) =387a(18) =388a(19) =788a(20) =887a(21) =888a(22) =1388a(23) =1788a(24) =1887a(25) =1888a(26) =2388a(27) =2788a(28) =2887a(29) =2888