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 A060198 #15 Feb 07 2025 15:33:47 %S A060198 1,16,240,3552,52224,764672,11163936,162631712,2365037376,34344187424, %T A060198 498139336992,7217820903328,104490673015136,1511512136496064, %U A060198 21849735526096256,315654728421607968,4557598148470097472,65771755517857808768,948727279133187672224,13679121303056997294080,197153311343380929158240 %N A060198 Dimensions of graded algebra associated with forest meanders. %C A060198 Number of meander slices with 2n crossings which can be open on both sides and whose loops are all even. A loop is even if it has its least point at an even index with crossings numbered from zero. This definition excludes slices such as (open, open, close, close) since the inner loop is not even. It also excludes (up, open, close, down) even though the loop is not contained in another. - _Andrew Howroyd_, Feb 07 2025 %H A060198 Roland Bacher, <a href="https://www-fourier.ujf-grenoble.fr/sites/default/files/ref_478.pdf">Meander algebras</a>, Institut Fourier, UMR 5582, Laboratoire de Mathématiques, 1999. %e A060198 a(1) = 240 = 256 - 16 = 4^4 - 4^2 counts all length 4 sequences of open, close, up and down steps, excluding those that have an open + close pair as the central two elements. - _Andrew Howroyd_, Feb 07 2025 %Y A060198 Meander sequences in Bacher's paper: A005315, A060066, A060089, A060111, A060148, A060149, A060174, A060198, A060206. %K A060198 nonn %O A060198 0,2 %A A060198 _N. J. A. Sloane_, Apr 10 2001 %E A060198 Offset corrected and a(7) onwards from _Andrew Howroyd_, Feb 06 2025