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 A209660 #33 Jan 31 2025 17:37:03 %S A209660 1,1,2,4,10,23,63,155,448,1152,3452,9158,28178,76539,240370,665128, %T A209660 2123437,5964658,19302248,54897742,179695133,516457890,1707112980, %U A209660 4950547189,16502992754,48230509790,161979310981,476609746441,1611226513378,4769315213007,16217954185533 %N A209660 Meandric numbers for a river crossing up to 14 parallel roads at n points. %C A209660 Number of ways that a river (or directed line) that starts in the South and flows East can cross up to 14 parallel East-West roads n times. %C A209660 Sequence derived from list of solutions described in A206432. %H A209660 Andrew Howroyd, <a href="/A209660/b209660.txt">Table of n, a(n) for n = 0..40</a> %Y A209660 Column k=14 of A380367. %Y A209660 Cf. A005316 (sequence for one road; extensive references and links). %Y A209660 Cf. A076876 (sequence for two parallel roads). %Y A209660 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 A209660 Cf. A206432 (sequence for unlimited number of parallel roads). %Y A209660 Cf. A076875, A076906, A076907. %K A209660 nonn %O A209660 0,3 %A A209660 _Robert Price_, May 07 2012 %E A209660 a(21) onwards from _Andrew Howroyd_, Jan 31 2025