a(0) = 0, a(n) = previous term + repunit of length of previous term for n > 0.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =5a(6) =6a(7) =7a(8) =8a(9) =9a(10) =10a(11) =21a(12) =32a(13) =43a(14) =54a(15) =65a(16) =76a(17) =87a(18) =98a(19) =109a(20) =220a(21) =331a(22) =442a(23) =553a(24) =664a(25) =775a(26) =886a(27) =997a(28) =1108a(29) =2219