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Search: id:A116387
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| A116387 |
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Expansion of 1/(sqrt(1-2x-3x^2)(2-M(x))), where M(x) is the g.f. of the Motzkin numbers A001006. |
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+0
3
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| 1, 2, 7, 22, 72, 234, 763, 2486, 8099, 26372, 85833, 279226, 907946, 2951066, 9587981, 31140034, 101104048, 328162170, 1064856217, 3454513274, 11204337056, 36332719182, 117795920249, 381848062066, 1237615088203, 4010710218384
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OFFSET
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0,2
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COMMENT
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Binomial transform of A116383.
The substitution x-> x/(1+x+x^2) in the g.f. (this might be called an inverse Motzkin transform) yields the g.f. of A074331. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 10 2008]
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FORMULA
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a(n)=sum{k=0..n, sum{j=0..n, C(n,j-k)C(j,n-j)}}.
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CROSSREFS
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Sequence in context: A092690 A030186 A162770 this_sequence A114495 A137398 A151439
Adjacent sequences: A116384 A116385 A116386 this_sequence A116388 A116389 A116390
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Feb 12 2006
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