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A168049 Expansion of (3-x-sqrt(1-2x-3x^2))/2. 4
1, 0, 1, 1, 2, 4, 9, 21, 51, 127, 323, 835, 2188, 5798, 15511, 41835, 113634, 310572, 853467, 2356779, 6536382, 18199284, 50852019, 142547559, 400763223, 1129760415, 3192727797, 9043402501, 25669818476, 73007772802, 208023278209 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

A variant of the Motzkin numbers A001006. Hankel transform is A168050.

Essentially the same as A086246. - R. J. Mathar, Dec 20 2011

LINKS

Table of n, a(n) for n=0..30.

FORMULA

Conjecture: n*a(n) +(3-2n)*a(n-1) +3(3-n)*a(n-2)=0. - R. J. Mathar, Dec 20 2011

CROSSREFS

Cf. A168051.

Sequence in context: A094288 A168051 A166587 * A001006 A086246 A027057

Adjacent sequences:  A168046 A168047 A168048 * A168050 A168051 A168052

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Nov 17 2009

STATUS

approved

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Last modified May 21 07:04 EDT 2013. Contains 225477 sequences.