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Label a 1-cm ruler with digits 1 cm wide.
1

%I #31 Jul 26 2022 10:09:07

%S 0,1,2,3,4,5,6,7,8,9,1,0,1,2,1,4,1,6,1,8,2,0,2,2,2,4,2,6,2,8,3,0,3,2,

%T 3,4,3,6,3,8,4,0,4,2,4,4,4,6,4,8,5,0,5,2,5,4,5,6,5,8,6,0,6,2,6,4,6,6,

%U 6,8,7,0,7,2,7,4,7,6,7,8,8,0,8,2,8,4,8,6,8,8,9,0,9,2,9,4,9,6,9,8,1,0,0,1,0,3

%N Label a 1-cm ruler with digits 1 cm wide.

%C The initial cm 0-9 can each be labeled because the labels take up one cm each, but the label for cm 10 takes up 2 cm, so cm 11 does not have its own label. Now 12 is labeled. This continues until cm 100 is labeled, which takes up 3 spaces, so 101 and 102 do not have their own label. - _John Cerkan_, Feb 14 2017

%C Or, let a'(n) be the length of all previous numbers in a(n), concatenated, then a(n) is a list of all the digits of each term of a'(n). - _John Cerkan_, Feb 16 2017

%C This sequence corresponds to the decimal digits of the terms of A088235. - _Rémy Sigrist_, Sep 25 2021

%H John Cerkan, <a href="/A001073/b001073.txt">Table of n, a(n) for n = 0..10000</a>

%t nmax = 105; f[0] = 0; f[n_] := f[n] = f[n-1] + Length[IntegerDigits[f[n-1]]]; digits = Table[IntegerDigits[f[n]], {n, 0, nmax}] // Flatten; a[n_] := digits[[n+1]]; Table[a[n], {n, 0, nmax}] (* _Jean-François Alcover_, Nov 26 2013 *)

%o (Python)

%o from itertools import islice

%o def agen():

%o an = 0

%o while True: s = str(an); yield from map(int, s); an += len(s)

%o print(list(islice(agen(), 67))) # _Michael S. Branicky_, Jul 26 2022

%Y Cf. A088235.

%K nonn,base,nice

%O 0,3

%A R. Lozyniak (11(AT)onna.com)