a(n) = 100^[n/10] + 2*n*10^[n/10]: inspired by Engel expansion of Pi.

Terms

a(0) =1a(1) =3a(2) =5a(3) =7a(4) =9a(5) =11a(6) =13a(7) =15a(8) =17a(9) =19a(10) =300a(11) =320a(12) =340a(13) =360a(14) =380a(15) =400a(16) =420a(17) =440a(18) =460a(19) =480a(20) =14000a(21) =14200a(22) =14400a(23) =14600a(24) =14800a(25) =15000a(26) =15200a(27) =15400a(28) =15600a(29) =15800