OFFSET
0,3
COMMENTS
Number of quasilinear weak orderings R on {1,...,n} and for which {1,...,n} has exactly one maximal element for the quasilinear weak ordering R.
Essentially the same as A038156. - R. J. Mathar, Jan 02 2018
LINKS
J. Devillet, Bisymmetric and quasitrivial operations: characterizations and enumerations, [math.RA] arXiv:1712.07856 (2017).
FORMULA
a(n) = A002627(n)-1, a(0)=0, a(1)=1.
MATHEMATICA
Join[{0, 1}, Drop[With[{nn=30}, CoefficientList[Series[(x*Exp[x]-1)/(1-x), {x, 0, nn}], x] Range[0, nn]!], 2]] (* Harvey P. Dale, Apr 02 2018 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
J. Devillet, Dec 22 2017
STATUS
approved