OFFSET
2,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 2..180
EXAMPLE
a(2) = 2: [1,1], [2,2].
a(4) = 12: [1,1,2,2], [1,1,3,3], [1,1,4,4], [2,2,1,1], [2,2,3,3], [2,2,4,4], [3,3,1,1], [3,3,2,2], [3,3,4,4], [4,4,1,1], [4,4,2,2], [4,4,3,3].
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 28 2013
STATUS
approved