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Search: id:A026125
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A026125 a(n) = number of (s(0),s(1),...,s(n)) such that every s(i) is a nonnegative integer, s(0) = 1, s(n) = 4, |s(1) - s(0)| = 1, |s(i) - s(i-1)| <= 1 for i >= 2. Also a(n) = T(n,n-3), where T is the array in A026120. +0
4
1, 3, 11, 35, 110, 336, 1013, 3021, 8945, 26345, 77297, 226161, 660387, 1925535, 5608710, 16325814, 47500227, 138168589, 401865485, 1168854085, 3400065944, 9892187162, 28787163584, 83796367200, 243997380575, 710704813221, 2070833535813 (list; graph; listen)
OFFSET

3,2

FORMULA

G.f.: z^3(1-z)^2M^5, with M the g.f. of the Motzkin numbers (A001006).

CROSSREFS

First differences of A026110.

Sequence in context: A027060 A126939 A126940 this_sequence A026154 A025181 A004054

Adjacent sequences: A026122 A026123 A026124 this_sequence A026126 A026127 A026128

KEYWORD

nonn

AUTHOR

Clark Kimberling (ck6(AT)evansville.edu)

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Last modified December 10 00:48 EST 2009. Contains 170565 sequences.


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