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A121285
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a(0) = 1; for n>0, a(n) = (n+3)*2^(n-2)-n*binomial(n-1, floor( (n-1)/2 ))-(n-1)*binomial(n-2,floor((n-2)/2)).
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0
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1, 1, 2, 4, 10, 22, 54, 120, 284, 626, 1438, 3136, 7044, 15212, 33596, 71952, 156856, 333610, 719886, 1522224, 3257972, 6855476, 14574772, 30541264, 64571400, 134827252, 283727564, 590608960, 1237926184, 2569953496, 5368225848, 11118205088, 23155034480, 47856472218
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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REFERENCES
| A. Bernini, F. Disanto, R. Pinzani and S. Rinaldi, Permutations defining convex permutominoes, preprint, 2007. [See S_{n+1}.]
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MATHEMATICA
| Join[{1}, Table[((n+3)2^(n-2))-(n Binomial[n-1, Floor[(n-1)/2]]) -((n-1)Binomial[n-2, Floor[(n-2)/2]]), {n, 50}]] (* From Harvey P. Dale, Mar 17 2011 *)
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CROSSREFS
| Sequence in context: A075560 A078040 A164990 * A030234 A205490 A205499
Adjacent sequences: A121282 A121283 A121284 * A121286 A121287 A121288
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jul 28 2007
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