OFFSET
3,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 3..600
Wikipedia, Coprime integers
Wikipedia, Partition of a set
EXAMPLE
a(3) = 1: 1|2|3.
a(4) = 6: 12|3|4, 13|2|4, 1|23|4, 14|2|3, 1|24|3, 1|2|34.
a(5) = 10: 123|4|5, 124|3|5, 125|3|4, 134|2|5, 135|2|4, 1|234|5, 1|235|4, 145|2|3, 1|245|3, 1|2|345.
a(7) = 21: 12345|6|7, 12346|5|7, 12347|5|6, 12356|4|7, 12357|4|6, 12367|4|5, 12456|3|7, 12457|3|6, 12467|3|5, 12567|3|4, 13456|2|7, 13457|2|6, 13467|2|5, 13567|2|4, 1|23456|7, 1|23457|6, 1|23467|5, 1|23567|4, 14567|2|3, 1|24567|3, 1|2|34567.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jan 09 2017
STATUS
approved