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A157143 A transform of the Motzkin numbers. 1
1, -1, -1, 0, 2, 1, -1, -4, -2, 5, 11, 0, -21, -24, 18, 68, 42, -100, -203, -17, 428, 521, -340, -1544, -1019, 2252, 4892, 606, -10297, -13331, 7821, 39310, 28028, -56893, -130394, -22239, 272991, 370641, -193874, -1081694, -821669 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Hankel transform is A157144.

LINKS

Table of n, a(n) for n=0..40.

FORMULA

G.f.: (1-x)/(1+x^2+x^3)*c((x/(1+x^2+x^3))^2), c(x) the g.f. of A000108.

a(n)=sum{k=0..n, (-1)^C(n-k+1,2)*C(floor((n-k)/2),k)*A001006(k)}.

CROSSREFS

Sequence in context: A123199 A212282 A157125 * A112096 A217874 A229118

Adjacent sequences:  A157140 A157141 A157142 * A157144 A157145 A157146

KEYWORD

easy,sign

AUTHOR

Paul Barry, Feb 24 2009

STATUS

approved

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Last modified April 19 03:33 EDT 2014. Contains 240738 sequences.