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A375615
Lexicographically earliest sequence of distinct positive integers such that for any n > 0, n * a(n) belongs to A055932.
2
1, 2, 4, 3, 6, 5, 30, 8, 10, 9, 210, 12, 2310, 15, 14, 16, 30030, 18, 510510, 21, 20, 105, 9699690, 24, 36, 1155, 32, 45, 223092870, 7, 6469693230, 27, 70, 15015, 42, 25, 200560490130, 255255, 770, 48, 7420738134810, 35, 304250263527210, 315, 28, 4849845
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).
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