Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #6 Oct 21 2021 01:03:29
%S 1,10,109,109108,109108109107,109108109107109108109106,
%T 109108109107109108109106109108109107109108109105,
%U 109108109107109108109106109108109107109108109105109108109107109108109106109108109107109108109104
%N a(0)=1; for n >= 0, a(n+1) is the concatenation of a(n) and a(n)-1.
%t Nest[Append[#1, #2*10^IntegerLength[#3] + #3] & @@ {#, #[[-1]], #[[-1]] - 1} &, {1, 10}, 6] (* _Michael De Vlieger_, Oct 20 2021 *)
%Y Suggested by A033564.
%K nonn,base
%O 0,2
%A _N. J. A. Sloane_, Oct 20 2021