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A376686 a(n) is the unique k such that A376677(k) is the reversal of A376677(n), or -1 if no such k exists.

%I A376686 #8 Oct 03 2024 11:03:38
%S A376686 1,2,3,5,4,6,10,8,12,7,11,9,15,21,13,19,17,18,16,22,14,20,23,32,28,30,
%T A376686 35,25,33,26,34,24,29,31,27,36,46,53,50,40,52,44,48,42,54,37,49,43,47,
%U A376686 39,51,41,38,45,60,76,66,63,79,55,71,65,58,74,62,57,67
%N A376686 a(n) is the unique k such that A376677(k) is the reversal of A376677(n), or -1 if no such k exists.
%C A376686 Is this sequence a permutation of the positive integers?
%H A376686 Rémy Sigrist, <a href="/A376686/b376686.txt">Table of n, a(n) for n = 1..10304</a>
%H A376686 Rémy Sigrist, <a href="/A376686/a376686.gp.txt">PARI program</a>
%H A376686 <a href="/index/K#Kolakoski">Index entries for sequences related to Kolakoski sequence</a>
%e A376686 The first terms, alongside the corresponding terms of A376677, are:
%e A376686   n   a(n)  A376677(n)  A376677(a(n))
%e A376686   --  ----  ----------  -------------
%e A376686    1     1           1              1
%e A376686    2     2           2              2
%e A376686    3     3          11             11
%e A376686    4     5          12             21
%e A376686    5     4          21             12
%e A376686    6     6          22             22
%e A376686    7    10         112            211
%e A376686    8     8         121            121
%e A376686    9    12         122            221
%e A376686   10     7         211            112
%e A376686   11    11         212            212
%e A376686   12     9         221            122
%e A376686   13    15        1121           1211
%e A376686   14    21        1122           2211
%e A376686   15    13        1211           1121
%e A376686   16    19        1212           2121
%o A376686 (PARI) \\ See Links section.
%Y A376686 Cf. A000002, A376677, A376685.
%K A376686 nonn,base
%O A376686 1,2
%A A376686 _Rémy Sigrist_, Oct 01 2024