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 A246829 #26 Feb 16 2025 08:33:23 %S A246829 1,1,2,3,7,16,45,111,318,881,2686,8033,25470,80480,263977,862865, %T A246829 2891344,9706757,33178076,113784968,395303480,1379160685,4859274472, %U A246829 17195407935,61310096228,219520467207,790749207801,2859542098634,10391610220375,37897965144166 %N A246829 The number of binary heaps on n elements whose breadth-first search reading word avoids 321. %C A246829 Note that a breadth-first search reading word is equivalent to reading the tree labels left to right by levels, starting with the root. %C A246829 For more information on heaps, see A056971. %H A246829 D. Levin, L. Pudwell, M. Riehl, A. Sandberg, <a href="http://www.etsu.edu/cas/math/pp2014/documents/talks/riehl.pdf">Pattern Avoidance on k-ary Heaps</a>, Slides of Talk, 2014. [broken link] %H A246829 Manda Riehl (joint work with Derek Levin, Lara Pudwell, and Adam Sandberg), <a href="/A246747/a246747_1.png">Page 92 of the Permutation Patterns 2014 Abstract Book</a> %H A246829 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Heap.html">Heap</a> %e A246829 A heap on 4 elements is pictured in the 2nd link, and has breadth first reading word abcd. Then for n = 4 the a(4) = 3 heaps have reading words 1234, 1243, and 1324. %Y A246829 Cf. A056971, A246747. %K A246829 nonn %O A246829 1,3 %A A246829 _Manda Riehl_, Sep 04 2014