OFFSET
1,2
LINKS
Donghwi Park, Source code for a(1) to a(5).
EXAMPLE
For n = 2 the a(2) = 3 solutions are (1 2; 3 4), (1 2; 4 3) and (1 3; 4 2).
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Donghwi Park, Jun 26 2022
STATUS
approved