OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..365
FORMULA
EXAMPLE
a(0) = 1: 1.
a(1) = 2: 132, 231.
a(2) = 15: 12435, 12534, 12543, 13425, 13524, 13542, 14523, 14532, 23415, 23514, 23541, 24513, 24531, 34512, 34521.
MAPLE
a:= proc(n) option remember; `if`(n<2, n+1,
2*(n+1)*(2*n+1)*a(n-1)/(n+2))
end:
seq(a(n), n=0..20);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Sep 08 2015
STATUS
approved