login
Number of Motzkin trees that are "untypable closable skeletons".
0

%I #7 Feb 27 2018 03:40:33

%S 0,0,0,1,0,2,9,10,41,128,258,821,2360,5813,17185,48721,129678,374519

%N Number of Motzkin trees that are "untypable closable skeletons".

%C From the Bodini-Tarau paper: a Motzkin skeleton is called "typable" if "it exists at least one simply-typed closed lambda term having it as its skeleton. An untypable skeleton is a closable skeleton for which no such term exists."

%H Olivier Bodini, Paul Tarau, <a href="https://arxiv.org/abs/1709.04302">On Uniquely Closable and Uniquely Typable Skeletons of Lambda Terms</a>, arXiv:1709.04302 [cs.PL], 2017.

%Y Cf. A000108, A001006, A135501.

%K nonn,more

%O 0,6

%A _Michael De Vlieger_, Feb 25 2018