A303166 - OEIS

%I #14 Apr 08 2020 14:08:38

%S 0,1,2,3,4,5,6,7,70,71,8,72,9,17,10,11,73,12,13,74,14,15,27,16,18,19,

%T 37,20,21,22,47,75,23,24,25,76,78,26,28,29,57,30,31,32,67,33,79,34,35,

%U 36,38,707,39,40,41,87,97,717,170,42,43,44,700,171,701,727,45,172,46,48,49,702,50,737,51

%N Lexicographically earliest sequence of distinct terms such that the successive quantities of digits between two successive 7's are given by the succession of the sequence's digits itself.

%C The sequence starts with a(1) = 0 and is always extended with the smallest integer not yet present that doesn't lead to a contradiction. This sequence is a permutation of the numbers >= 0.

%H Jean-Marc Falcoz, <a href="/A303166/b303166.txt">Table of n, a(n) for n = 1..1208</a>

%e There are:

%e 0 digit  between the 7 of "7" and the 7 of "70";

%e 1 digit  between the 7 of "70" and the 7 of "71";

%e 2 digits between the 7 of "71" and the 7 of "72";

%e 3 digits between the 7 of "72" and the 7 of "17";

%e 4 digits between the 7 of "17" and the 7 of "73";

%e 5 digits between the 7 of "73" and the 7 of "74";

%e 6 digits between the 7 of "74" and the 7 of "27";

%e 7 digits between the 7 of "27" and the 7 of "37";

%e 7 digits between the 7 of "37" and the 7 of "47";

%e 0 digit  between the 7 of "47" and the 7 of "75";

%e 7 digits between the 7 of "75" and the 7 of "76";

%e 1 digit  between the 7 of "76" and the 7 of "78";

%e etc.

%e We see that the first column here is the succession of the digits of the sequence, as well as the size of each chunk of digits between two successive 7's.

%Y Cf. A303151 for the same idea with 1's as chunk's separators, A303157 with 2's, A303158 with 3's, A302943 with 4's, A303163 with 5's, A303164 with 6's, A303167 with 8's and A303171 with 9's.

%K nonn,base

%O 1,3

%A _Eric Angelini_ and _Jean-Marc Falcoz_, Apr 19 2018