cp's OEIS Frontend

A330384 Single-digit numbers in order of appearance in decimal expansions of composite numbers, followed by two-digit numbers in order of appearance, then three-digit numbers and so forth.

%I A330384 #30 Aug 14 2025 04:25:16
%S A330384 4,6,8,9,1,0,2,5,7,3,10,12,14,15,16,18,20,21,22,24,25,26,27,28,30,32,
%T A330384 33,34,35,36,38,39,40,42,44,45,46,48,49,50,51,52,54,55,56,57,58,60,62,
%U A330384 63,64,65,66,68,69,70,72,74,75,76,77,78,80,81,82,84,85,86
%N A330384 Single-digit numbers in order of appearance in decimal expansions of composite numbers, followed by two-digit numbers in order of appearance, then three-digit numbers and so forth.
%H A330384 Rémy Sigrist, <a href="/A330384/b330384.txt">Table of n, a(n) for n = 1..11000</a>
%H A330384 Rémy Sigrist, <a href="/A330384/a330384.png">Colored scatterplot of the first 110000 terms</a> (red pixels indicate terms that are prime)
%H A330384 Rémy Sigrist, <a href="/A330384/a330384.gp.txt">PARI program for A330384</a>
%e A330384 From _Rémy Sigrist_, Dec 24 2019: (Start)
%e A330384 The first terms, alongside the corresponding composite numbers, are:
%e A330384   n   a(n)  Composite
%e A330384   --  ----  ---------
%e A330384    1     4          4
%e A330384    2     6          6
%e A330384    3     8          8
%e A330384    4     9          9
%e A330384    5     1         10
%e A330384    6     0         10
%e A330384    7     2         12
%e A330384    8     5         15
%e A330384    9     7         27
%e A330384   10     3         30
%e A330384   11    10         10
%e A330384   12    12         12
%e A330384   13    14         14
%e A330384   ...
%e A330384   79    99         99
%e A330384   80    11        110
%e A330384   81    17        117
%e A330384   82    19        119
%e A330384   83    23        123
%e A330384 (End)
%o A330384 (PARI) \\ See Links section.
%Y A330384 Cf. A002808, A321043, A321128.
%K A330384 nonn,base,look
%O A330384 1,1
%A A330384 _David Williams_, Dec 12 2019
%E A330384 More terms from _Rémy Sigrist_, Dec 24 2019