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A152983
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Number of divisors of Motzkin number A001006(n).
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2
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1, 1, 2, 3, 3, 4, 4, 2, 4, 4, 6, 8, 2, 8, 24, 18, 4, 16, 8, 12, 16, 24, 48, 72, 12, 8, 6, 16, 8, 16, 8, 12, 4, 16, 64, 12, 2, 8, 8, 8, 8, 24, 96, 96, 6, 24, 72, 48, 24, 32, 128, 96, 16, 8, 8, 8, 16, 128, 60, 192, 6, 32, 32, 96, 8, 96, 512, 36, 24, 16, 24, 384, 24, 96, 144, 48, 64, 64, 32
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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FORMULA
| a(n) = A000005(A001006(n)).
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EXAMPLE
| a(5)=4 because the Motzkin number M(5)=21 has 4 divisors: 1,3,7 and 21. [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 14 2009]
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MAPLE
| with(numtheory): M := proc (n) options operator, arrow: (sum((-1)^j*binomial(n+1, j)*binomial(2*n-3*j, n), j = 0 .. floor((1/3)*n)))/(n+1) end proc: seq(tau(M(n)), n = 0 .. 82); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 14 2009]
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CROSSREFS
| Cf. A000005, A001006, A152763.
Sequence in context: A186971 A096827 A063826 * A205324 A132983 A029133
Adjacent sequences: A152980 A152981 A152982 * A152984 A152985 A152986
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KEYWORD
| nonn
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AUTHOR
| Omar E. Pol (info(AT)polprimos.com), Dec 20 2008
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EXTENSIONS
| Extended by Emeric Deutsch (deutsch(AT)duke.poly.edu), Jan 14 2009
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