A374611 - OEIS

%I #10 Jul 17 2024 15:56:31

%S 1,3,2,7,9,6,4,13,5,19,21,14,8,12,18,27,29,15,10,37,11,39,43,26,49,24,

%T 16,28,17,38,53,57,42,61,36,35,20,30,22,63,71,33,23,79,45,81,87,54,25,

%U 89,58,56,31,48,91,52,32,51,101,74,34,107,40,111,72,78

%N If n = A066207(i) * A066208(j) for some i, j > 0 then a(n) = A066207(j) * A066208(i).

%C This sequence is a self-inverse permutation of the positive integers with infinitely many fixed points.

%H Rémy Sigrist, <a href="/A374611/b374611.txt">Table of n, a(n) for n = 1..10000</a>

%H Rémy Sigrist, <a href="/A374611/a374611.gp.txt">PARI program</a>

%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>

%F a(A360646(n, k)) = A360646(k, n).

%F a(n) = n iff n = A066207(k) * A066208(k) for some k > 0.

%e For n = 42: 42 = 21 * 2 = A066207(7) * A066208(2), so a(42) = A066207(2) * A066208(7) = 3 * 11 = 33.

%o (PARI) \\ See Links section.

%Y See A374600 for a similar sequence.

%Y Cf. A066207, A066208, A247503, A248101, A360646.

%K nonn

%O 1,2

%A _Rémy Sigrist_, Jul 14 2024