OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
EXAMPLE
a(2) = 5: {1,2}, {1,5}, {2,4}, {3,6}, {4,5}.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 29 2018
STATUS
approved