OFFSET
1,2
COMMENTS
This sequence is a self-inverse permutation of the positive integers.
The n-th term is a multiple of A083720(n).
LINKS
EXAMPLE
The first terms, alongside the primes factors of n*a(n), are:
n a(n) Primes factors
-- ---- --------------------
1 1 {}
2 2 {2}
3 4 {2, 3}
4 3 {2, 3}
5 6 {2, 3, 5}
6 5 {2, 3, 5}
7 30 {2, 3, 5, 7}
8 8 {2}
9 10 {2, 3, 5}
10 9 {2, 3, 5}
11 210 {2, 3, 5, 7, 11}
12 12 {2, 3}
13 2310 {2, 3, 5, 7, 11, 13}
14 15 {2, 3, 5, 7}
15 14 {2, 3, 5, 7}
PROG
(PARI) \\ See Links section.
CROSSREFS
KEYWORD
nonn
AUTHOR
Rémy Sigrist, Aug 21 2024
STATUS
approved