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 A209707 #34 Jan 31 2025 17:22:45 %S A209707 1,1,2,4,10,23,63,155,448,1152,3452,9158,28178,76539,240370,665129, %T A209707 2123438,5964689,19302281,54898345,179695808,516467363,1707124038, %U A209707 4950679082,16503152306,48232213024,161981435856,476630676669,1611253336964,4769563838975,16218280461398 %N A209707 Meandric numbers for a river crossing up to 15 parallel roads at n points. %C A209707 Number of ways that a river (or directed line) that starts in the South and flows East can cross up to 15 parallel East-West roads n times. %C A209707 Sequence derived from list of solutions described in A206432. %H A209707 Andrew Howroyd, <a href="/A209707/b209707.txt">Table of n, a(n) for n = 0..40</a> %Y A209707 Column k=15 of A380367. %Y A209707 Cf. A005316 (sequence for one road; extensive references and links). %Y A209707 Cf. A076876 (sequence for two parallel roads). %Y A209707 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 A209707 Cf. A206432 (sequence for unlimited number of parallel roads). %Y A209707 Cf. A076875, A076906, A076907. %K A209707 nonn %O A209707 0,3 %A A209707 _Robert Price_, May 07 2012 %E A209707 a(21) onwards from _Andrew Howroyd_, Jan 31 2025