1,2

Khamis, Soheir M., Height counting of unlabeled interval and N-free posets. Discrete Math. 275 (2004), no. 1-3, 165-175.

Table of n, a(n) for n=1..13.

Row sums of A202181.

From the definition, this sequence should be the same as A003430. I do not understand why they differ - possibly a different definition of "N-free"?

Sequence in context: A000734 A148366 A005751 * A149944 A149945 A149946

Adjacent sequences: A202179 A202180 A202181 * A202183 A202184 A202185

nonn

N. J. A. Sloane, Dec 13 2011

approved