A336954 - OEIS

%I #12 Aug 11 2020 01:34:32

%S 1,10,2,3,20,30,4,5,6,7,40,50,60,70,8,9,11,12,32,83,90,22,220,21,13,

%T 33,333,23,24,25,34,43,52,42,26,27,28,36,63,71,18,61,14,29,240,31,130,

%U 91,15,35,53,54,55,44,37,430,41,17,45,38,93,51,16,48,49,46

%N Lexicographically earliest sequence of distinct positive terms such that, in the concatenation of the decimal representations of the terms, for any digit d at position p, d appears at some position q such that abs(p-q) = d.

%C This sequence combines features of A322467 and of A336880.

%C Some numbers, like 121, cannot appear in this sequence.

%H Rémy Sigrist, <a href="/A336954/b336954.txt">Table of n, a(n) for n = 1..10000</a>

%H Rémy Sigrist, <a href="/A336954/a336954.gp.txt">PARI program for A336954</a>

%e For n = 1:

%e - we can choose a(1) = 1.

%e For n = 2:

%e - a(2) must start with a digit 1,

%e - we can choose a(2) = 10.

%e For n = 3:

%e - we can choose a(3) = 2.

%e For n = 4:

%e - we can choose a(4) = 3.

%e For n = 5:

%e - a(5) must start with a digit 2,

%e - we cab choose a(5) = 20.

%o (PARI) See Links section.

%Y Cf. A322467, A336880.

%K nonn,base

%O 1,2

%A _Rémy Sigrist_, Aug 08 2020