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 A051485 #17 Jul 01 2025 19:27:36 %S A051485 0,1,1,2,6,14,32,74,180,457,1195,3177,8526,23018,62441,170153,465791, %T A051485 1280956,3538618,9817619,27348480,76467497,214532805,603732396, %U A051485 1703728554,4819990947,13667248631,38834528740,110556072877,315290709729,900635841754,2576615923655,7381956798465,21177682172332,60832837964492 %N A051485 Number of double nodes (exactly two nodes on that level) for all Motzkin paths of length n. %e A051485 Of the 9 Motzkin paths of length 4 the following 5 have a total of 6 double nodes: %e A051485 |1......| %e A051485 |2../\..|3..__..|2.._...|2..._..|2......| %e A051485 |2./..\.|2./..\.|3./.\_.|3._/.\.|3./\/\.| %Y A051485 Cf. A001006, A088457. %Y A051485 Column k=2 of A372014. %K A051485 nonn %O A051485 0,4 %A A051485 _Wenjin Woan_ %E A051485 Edited by _Michael Somos_, Sep 29 2003 %E A051485 a(16)-a(34) from _Alois P. Heinz_, Apr 13 2024