OFFSET
0,5
LINKS
Wikipedia, Permutation
EXAMPLE
a(3) = 1: (13)(2).
a(4) = 4: (124)(3), (142)(3), (13)(2)(4), (14)(2)(3).
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 17 2023
STATUS
approved