1,2

Cardinality of the set of nesting-similarity classes.

M. Klazar, On identities concerning the numbers of crossings and nestings of two edges in matchings

G.f.: C+z^2(2zC'+C)^2C, with C(z) the g.f. of the Catalan numbers.

Equals A006419(n-1) + A000108(n).

Sequence in context: A135343 A083314 A155179 this_sequence A081704 A166482 A007854

Adjacent sequences: A104265 A104266 A104267 this_sequence A104269 A104270 A104271

nonn,easy

Ralf Stephan, Apr 17 2005