A382377 Lexicographically earliest sequence of distinct positive integers such that the number of distinct prime factors of n and a(n) differ exactly by one.

2, 1, 6, 10, 12, 3, 14, 15, 18, 4, 20, 5, 21, 7, 8, 22, 24, 9, 26, 11, 13, 16, 28, 17, 33, 19, 34, 23, 35, 36, 38, 39, 25, 27, 29, 30, 40, 31, 32, 37, 44, 45, 46, 41, 42, 43, 48, 47, 50, 49, 53, 59, 51, 60, 61, 64, 66, 67, 52, 54, 55, 70, 71, 56, 73, 57, 58

Offset: 1

Author

Rémy Sigrist, Mar 23 2025

Keywords

• nonn

Comments

A self-inverse permutation of the positive integers.

Examples

			The initial terms are:
  n   a(n)  A001221(n)  A001221(a(n))
  --  ----  ----------  -------------
   1     2           0              1
   2     1           1              0
   3     6           1              2
   4    10           1              2
   5    12           1              2
   6     3           2              1
   7    14           1              2
   8    15           1              2
   9    18           1              2
  10     4           2              1
  11    20           1              2
  12     5           2              1
  13    21           1              2
  14     7           2              1
  15     8           2              1
		

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

Cf. A001221, A382375, A382376.

Programs

PARI

\\ See Links section.