cp's OEIS Frontend

A381081 Lexicographically earliest sequence of distinct positive integers such that the string value of a(n) begins with a divisor of a(n-1).

%I A381081 #8 Feb 13 2025 08:27:00
%S A381081 1,10,2,11,12,3,13,14,7,15,5,16,4,17,18,6,19,100,20,21,30,22,23,101,
%T A381081 102,24,8,25,50,26,27,9,31,103,104,28,29,105,32,40,41,106,53,107,108,
%U A381081 33,34,109,110,51,35,52,42,36,37,111,38,112,43,113,114,39,115,54,60,44,45,55,56,46,116,47,117,90,57,118,59,119,70,58,120,48,49,71,121,122
%N A381081 Lexicographically earliest sequence of distinct positive integers such that the string value of a(n) begins with a divisor of a(n-1).
%C A381081 The sequence contains many fixed points, these beginning 1, 22, 23, 40, 41, 52, 199, 1936, 1937, 1938, 1939, ... .
%H A381081 Scott R. Shannon, <a href="/A381081/b381081.txt">Table of n, a(n) for n = 1..10000</a>
%H A381081 Scott R. Shannon, <a href="/A381081/a381081.png">Image of the first 150000 terms</a>. The green line is a(n) = n.
%e A381081 a(2) = 10 as the only divisor of a(1) = 1 is 1, and 10 is the smallest unused number to begin with 1.
%e A381081 a(43) = 53 as a(42) = 106 whose divisors are 1, 2, 53, 106, and 53 is the smallest unused number to begin with 53 - all other smaller numbers beginning with 1 and 2 have been used. This is the first term to differ from A248024.
%Y A381081 Cf. A027750, A248024, A000030.
%K A381081 nonn,base,look
%O A381081 1,2
%A A381081 _Scott R. Shannon_, Feb 13 2025