OFFSET
3,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 3..1000
Wikipedia, Partition of a set
Index entries for linear recurrences with constant coefficients, signature (3,4,-18,1,33,-16,-18,12)
FORMULA
G.f.: (10*x^6 -x^5 -13*x^4 +x^3 +6*x^2-1) *x^3 / ((2*x-1) *(x+1) *(3*x^2-1) *(2*x^2-1) *(x-1)^2).
EXAMPLE
a(5) = 7: 123|4|5, 12|34|5, 12|3|45, 1|234|5, 145|2|3, 1|2|345, 1|23|45.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alois P. Heinz, Jun 10 2018
STATUS
approved