OFFSET
0,4
EXAMPLE
a(3) = 12: 121313232, 121323132, 121323231, 131213232, 132312132, 132323121, 231213132, 231213231, 231312132, 231323121, 232312131, 232313121.
a(4) = 761: 121213243434, 121214343423, 121313242434, 121313243424, ..., 343424121213, 343424121312, 343424131212, 343434121212.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Sep 08 2016
STATUS
approved