A051485 - OEIS

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

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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.