OFFSET
2,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 2..900
EXAMPLE
a(2) = 1: 12.
a(3) = 16: 112, 113, 121, 122, 131, 132, 133, 212, 213, 223, 231, 232, 233, 312, 313, 323.
a(4) = 175: 1112, 1113, 1114, 1121, ..., 4414, 4423, 4424, 4434.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Feb 15 2016
STATUS
approved