A051485 Number of double nodes (exactly two nodes on that level) for all Motzkin paths of length n.

0, 1, 1, 2, 6, 14, 32, 74, 180, 457, 1195, 3177, 8526, 23018, 62441, 170153, 465791, 1280956, 3538618, 9817619, 27348480, 76467497, 214532805, 603732396, 1703728554, 4819990947, 13667248631, 38834528740, 110556072877, 315290709729, 900635841754, 2576615923655, 7381956798465, 21177682172332, 60832837964492

Offset

0,4

Links

Table of n, a(n) for n=0..34.

Example

Of the 9 Motzkin paths of length 4 the following 5 have a total of 6 double nodes:
|1......|
|2../\..|3..__..|2.._...|2..._..|2......|
|2./..\.|2./..\.|3./.\_.|3._/.\.|3./\/\.|

Crossrefs

Cf. A001006, A088457.

Column k=2 of A372014.

Sequence in context: A131352 A232230 A294780 * A077999 A110524 A083404

Adjacent sequences: A051482 A051483 A051484 * A051486 A051487 A051488

Keyword

nonn

Author

Wenjin Woan

Extensions

Edited by Michael Somos, Sep 29, 2003

a(16)-a(34) from Alois P. Heinz, Apr 13 2024

Status

approved