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%I #19 Oct 16 2019 01:30:41
%S 1,2,10,3,20,4,5,30,6,7,40,8,50,9,11,60,12,70,21,41,80,22,23,90,42,24,
%T 13,25,14,15,26,16,17,27,18,19,28,100,29,31,43,200,51,32,61,44,33,45,
%U 52,53,34,62,46,35,47,54,55,36,63,48,37,49,56,57,38,64,400
%N A Skolem-type sequence: each pair of two terms that start with a digit k are separated by k other terms. Lexicographically earliest permutation of positive integers with this property.
%H Rémy Sigrist, <a href="/A247476/b247476.txt">Table of n, a(n) for n = 1..10000</a>
%H E. Angelini, <a href="http://seqfan.eu">A Skolem-like seq with no terms repeated</a>, SeqFan list, Nov 22 2014
%H Rémy Sigrist, <a href="/A247476/a247476.png">Illustration of first terms</a>
%H Rémy Sigrist, <a href="/A247476/a247476.gp.txt">PARI program for A247476</a>
%e The sequence starts 1,2,10,...: there is 1 term enclosed by 1 and 10: the term 2.
%e Then it goes on 1,2,10,3,20,...: there are 2 terms (10 and 3) enclosed between 2 and 20.
%e Then, in 1,2,10,3,20,4,5,30,... there are 3 terms (20, 4 and 5) enclosed by 3 and 30, etc.
%o (PARI) See Links section.
%K nonn,base,nice
%O 1,2
%A _Eric Angelini_ and _M. F. Hasler_, Nov 30 2014
%E Data corrected by _Rémy Sigrist_, Jul 10 2019
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