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A376685 a(n) is the unique k such that A376637(k) is the reversal of A376637(n).

%I A376685 #8 Oct 03 2024 11:03:34
%S A376685 1,2,3,5,4,6,9,10,7,8,13,15,11,16,12,14,19,21,17,23,18,24,20,22,27,28,
%T A376685 25,26,38,34,40,33,32,30,39,37,36,29,35,31,44,43,42,41,48,47,46,45,54,
%U A376685 53,56,55,50,49,52,51,59,60,57,58,62,61,64,63,67,68,65
%N A376685 a(n) is the unique k such that A376637(k) is the reversal of A376637(n).
%C A376685 This sequence is a self-inverse permutation of the positive integers.
%H A376685 Rémy Sigrist, <a href="/A376685/b376685.txt">Table of n, a(n) for n = 1..10048</a>
%H A376685 Rémy Sigrist, <a href="/A376685/a376685.gp.txt">PARI program</a>
%H A376685 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%F A376685 A376637(a(n)) = A004086(A376637(n)).
%e A376685 The first terms, alongside the corresponding terms of A376637, are:
%e A376685   n   a(n)  A376637(n)  A376637(a(n))
%e A376685   --  ----  ----------  -------------
%e A376685    1     1           1              1
%e A376685    2     2           2              2
%e A376685    3     3          11             11
%e A376685    4     5          12             21
%e A376685    5     4          21             12
%e A376685    6     6          22             22
%e A376685    7     9         112            211
%e A376685    8    10         122            221
%e A376685    9     7         211            112
%e A376685   10     8         221            122
%e A376685   11    13        1121           1211
%e A376685   12    15        1122           2211
%e A376685   13    11        1211           1121
%e A376685   14    16        2122           2212
%e A376685   15    12        2211           1122
%e A376685   16    14        2212           2122
%o A376685 (PARI) \\ See Links section.
%Y A376685 Cf. A004086, A376637, A376686.
%K A376685 nonn,base
%O A376685 1,2
%A A376685 _Rémy Sigrist_, Oct 01 2024