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 A206432 #22 Dec 12 2015 15:26:19 %S A206432 1,1,2,4,10,23,63,155,448,1152,3452,9158,28178,76539,240370,665129, %T A206432 2123439,5964691,19302316,54898417,179696559,516468945,1707136837, %U A206432 4950706599,16503343162,48232630706,161984048816,476636485050,1611287098347,4769639932874,16218699278307 %N A206432 Meandric numbers for a river crossing any number of parallel roads at n points. %C A206432 Number of ways that a river (or directed line) that starts in the South and flows East can cross any number of parallel East-West roads n times. %C A206432 Of course, the number of roads crossed cannot be more than the number of crossings, n. %C A206432 A file (28GB) listing all solutions through n=20 is available from the author. %H A206432 Andrew Howroyd, <a href="/A206432/b206432.txt">Table of n, a(n) for n = 0..40</a> %Y A206432 Cf. A005316 (sequence for one road; extensive references and links). %Y A206432 Cf. A076876 (sequence for two parallel roads). %Y A206432 Cf. A204352, A208062, A208126, A208452, A208453, A209383, A209621, A209622, A209626, A209656, A209657, A209660, A209707, A210344, A210478, A210567, A210592 (sequences for 3 to 19 parallel roads). %Y A206432 Cf. A076875, A076906, A076907. %K A206432 nonn,nice %O A206432 0,3 %A A206432 _Robert Price_, May 07 2012 %E A206432 a(21)-a(30) from _Andrew Howroyd_, Dec 07 2015