OFFSET
2,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 2..1000
Index entries for linear recurrences with constant coefficients, signature (3,-1,0,-2,-3,1,1).
FORMULA
G.f.: x^3*(x^2-3)/((x^2+x-1)*(x^5-2*x^3-2*x+1)).
EXAMPLE
a(3) = 3: 231, 312, 321.
a(4) = 9: 1342, 1423, 1432, 2314, 2413, 3124, 3142, 3214, 3412.
a(5) = 23: 12453, 12534, 12543, 13425, 13524, 14235, 14253, 14325, 14523, 21453, 21534, 21543, 23145, 23154, 24135, 24153, 31245, 31254, 31425, 31524, 32145, 32154, 34125.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Jan 28 2019
STATUS
approved