A374611 If n = A066207(i) * A066208(j) for some i, j > 0 then a(n) = A066207(j) * A066208(i).

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, 16, 28, 17, 38, 53, 57, 42, 61, 36, 35, 20, 30, 22, 63, 71, 33, 23, 79, 45, 81, 87, 54, 25, 89, 58, 56, 31, 48, 91, 52, 32, 51, 101, 74, 34, 107, 40, 111, 72, 78

Offset: 1

Author

Rémy Sigrist, Jul 14 2024

Keywords

• nonn

Comments

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

Examples

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

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..10000
• Rémy Sigrist, PARI program
• Index entries for sequences that are permutations of the natural numbers

Crossrefs

See A374600 for a similar sequence.

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

Programs

PARI

\\ See Links section.

Formula

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

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