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 A208452 #20 Dec 06 2015 11:45:30 %S A208452 1,1,2,4,10,23,63,154,446,1135,3416,8947,27712,74204,235041,640552, %T A208452 2065849,5711840,18696838,52321747,173413647,490279035,1642287831, %U A208452 4684178185,15834649146,45511151647,155077912223,448722569787,1539743907074,4481866870316,15474663284941 %N A208452 Meandric numbers for a river crossing up to 6 parallel roads at n points. %C A208452 Number of ways that a river (or directed line) that starts in the South and flows East can cross up to 6 parallel East-West roads n times. %C A208452 Sequence derived from list of solutions described in A206432. %H A208452 Andrew Howroyd, <a href="/A208452/b208452.txt">Table of n, a(n) for n = 0..36</a> %Y A208452 Cf. A005316 (sequence for one road; extensive references and links). %Y A208452 Cf. A076876 (sequence for two parallel roads). %Y A208452 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 A208452 Cf. A206432 (sequence for unlimited number of parallel roads). %Y A208452 Cf. A076875, A076906, A076907. %K A208452 nonn %O A208452 0,3 %A A208452 _Robert Price_, May 07 2012 %E A208452 a(21)-a(36) from _Andrew Howroyd_, Dec 05 2015