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%I #11 Jul 25 2020 11:44:44
%S 1,1,2,1,3,1,4,1,5,1,6,1,7,1,8,1,9,1,10,11,11,12,12,13,12,14,12,15,12,
%T 16,12,17,12,18,12,19,12,20,2,2,3,2,4,2,5,2,6,2,7,2,8,2,9,2,10,12,30,
%U 3,3,4,3,5,3,6,3,7,3,8,3,9,3,10,13,22,11,13,23
%N a(1) = 1, and for any n > 0, a(n+1) is the number of k in the range 1..n such that the decimal representation of a(k) appears as a substring in the decimal representation of a(n).
%C This sequence is unbounded.
%H Rémy Sigrist, <a href="/A336514/b336514.txt">Table of n, a(n) for n = 1..10000</a>
%H Rémy Sigrist, <a href="/A336514/a336514.png">Density plot of the first 100000000 terms</a>
%H Rémy Sigrist, <a href="/A336514/a336514.gp.txt">PARI program for A336514</a>
%e The first terms, alongside the corresponding k's, are:
%e n a(n) k's
%e -- ---- -----------
%e 1 1 N/A
%e 2 1 {1}
%e 3 2 {1, 2}
%e 4 1 {3}
%e 5 3 {1, 2, 4}
%e 6 1 {5}
%e 7 4 {1, 2, 4, 6}
%e 8 1 {7}
%e 9 5 {1, 2, 4, 6, 8}
%e 10 1 {9}
%o (PARI) See Links section.
%Y Cf. A336515 (binary variant).
%K nonn,look,base
%O 1,3
%A _Rémy Sigrist_, Jul 24 2020
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