This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A300129 #7 Feb 27 2018 03:40:33 %S A300129 0,0,0,1,0,2,9,10,41,128,258,821,2360,5813,17185,48721,129678,374519 %N A300129 Number of Motzkin trees that are "untypable closable skeletons". %C A300129 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 A300129 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 A300129 Cf. A000108, A001006, A135501. %K A300129 nonn,more %O A300129 0,6 %A A300129 _Michael De Vlieger_, Feb 25 2018