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 A210567 #26 Jan 31 2025 17:21:57 %S A210567 1,1,2,4,10,23,63,155,448,1152,3452,9158,28178,76539,240370,665129, %T A210567 2123439,5964691,19302316,54898416,179696557,516468904,1707136753, %U A210567 4950705596,16503341064,48232611611,161984008143,476636172048,1611286420859,4769635283158,16218689069176 %N A210567 Meandric numbers for a river crossing up to 18 parallel roads at n points. %C A210567 Number of ways that a river (or directed line) that starts in the South and flows East can cross up to 18 parallel East-West roads n times. %C A210567 Sequence derived from list of solutions described in A206432. %H A210567 Andrew Howroyd, <a href="/A210567/b210567.txt">Table of n, a(n) for n = 0..40</a> %Y A210567 Column k=18 of A380367. %Y A210567 Cf. A005316 (sequence for one road; extensive references and links). %Y A210567 Cf. A076876 (sequence for two parallel roads). %Y A210567 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 A210567 Cf. A206432 (sequence for unlimited number of parallel roads). %Y A210567 Cf. A076875, A076906, A076907. %K A210567 nonn %O A210567 0,3 %A A210567 _Robert Price_, May 07 2012 %E A210567 a(21) onwards from _Andrew Howroyd_, Jan 31 2025