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Search: id:A005324
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| 1, 5, 20, 70, 230, 726, 2235, 6765, 20240, 60060, 177177, 520455, 1524120, 4453320, 12991230, 37854954, 110218905, 320751445, 933149470, 2714401580, 7895719634, 22969224850, 66829893650, 194486929650, 566141346225, 1648500576021
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OFFSET
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4,2
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COMMENT
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a(n) = number of (s(0), s(1), ..., s(n)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| <= 1 for i = 1,2,...,n, s(0) = 0, s(n) = 4. - Clark Kimberling (ck6(AT)evansville.edu)
a(n) = T(n,n-4), where T is the array in A026300.
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. Donaghey and L. W. Shapiro, Motzkin numbers, J. Combin. Theory, Series A, 23 (1977), 291-301.
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FORMULA
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G.f.: z^4*M^5, where M is g.f. of Motzkin numbers (A001006).
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CROSSREFS
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Cf. A026300.
A diagonal of triangle A020474.
Sequence in context: A089094 A080930 A000343 this_sequence A154638 A054889 A056384
Adjacent sequences: A005321 A005322 A005323 this_sequence A005325 A005326 A005327
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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