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A252043 a(n) is the concatenation of first n terms of A033307.

%I A252043 #62 Oct 25 2022 10:19:54
%S A252043 1,12,123,1234,12345,123456,1234567,12345678,123456789,1234567891,
%T A252043 12345678910,123456789101,1234567891011,12345678910111,
%U A252043 123456789101112,1234567891011121,12345678910111213,123456789101112131,1234567891011121314
%N A252043 a(n) is the concatenation of first n terms of A033307.
%H A252043 Harvey P. Dale, <a href="/A252043/b252043.txt">Table of n, a(n) for n = 1..1000</a>
%F A252043 a(n) = floor(C*10^n) with C the Champernowne constant, 0.123456789101112131415..., A033307.
%F A252043 a(n) = floor(A007908(n)/10^n) For n>=10.
%e A252043 a(3)=123.
%p A252043 a[0]:= 0;
%p A252043 count:= 0:
%p A252043 for x from 1 to 30 do
%p A252043   L:= convert(x,base,10);
%p A252043   for i from 1 to nops(L) do
%p A252043     count:= count+1;
%p A252043     a[count]:= a[count-1]*10+L[-i];
%p A252043   od
%p A252043 od:
%p A252043 seq(a[i],i=1..count); # _Robert Israel_, Jan 11 2015
%t A252043 b[1] = 1
%t A252043 b[n_] := b[n - 1]*10^(Floor[Log[10, 10n]]) + n
%t A252043 Table[Floor[b[n] /10^(n)], {n, 10, 200}]
%t A252043 Module[{nn=20,ch},ch=RealDigits[ChampernowneNumber[],10,nn][[1]];Table[ FromDigits[ Take[ch,n]],{n,nn}]] (* _Harvey P. Dale_, Aug 31 2015 *)
%o A252043 (Python)
%o A252043 from itertools import islice
%o A252043 def bgen(): yield from (c for n in count(1) for c in str(n) )
%o A252043 def agen():
%o A252043     s, g = "", bgen()
%o A252043     while True:
%o A252043         s += next(g); yield int(s)
%o A252043 print(list(islice(agen(), 20))) # _Michael S. Branicky_, Oct 25 2022
%Y A252043 Cf. A007908 (concatenate 1 through n), A033307.
%K A252043 nonn,base
%O A252043 1,2
%A A252043 _José de Jesús Camacho Medina_, Dec 15 2014
%E A252043 Definition corrected by _Zak Seidov_, Jan 18 2015