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A032095
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Number of reversible strings with n-1 black beads and n-1 white beads. String is not palindromic.
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1
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1, 1, 2, 10, 32, 126, 452, 1716, 6400, 24310, 92252, 352716, 1351616, 5200300, 20056584, 77558760, 300533760, 1166803110, 4537543340, 17672631900, 68923172032, 269128937220, 1052049129144, 4116715363800
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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LINKS
| C. G. Bower, Transforms (2)
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FORMULA
| "BHK[ n ](2n-1)" (reversible, identity, unlabeled, n parts, 2n-1 elements) transform of 1, 1, 1, 1...
for n>1 a(n)=(1/2)*C(2n-2, n-1) if n is even, a(n)=(1/2)[C(2n-2, n-1)-C(n-1, (n-1)/2)] if n is odd. (Emeric Deutsch (deutsch(AT)duke.poly.edu) Jul 25 2002)
E.g.f. : 1+exp(x)*sinh(x)*BesselI(0,2x). [From Paul Barry (pbarry(AT)wit.ie), Aug 11 2009]
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CROSSREFS
| Central column of triangle A034877.
Sequence in context: A034555 A084154 A083099 * A151019 A004028 A080668
Adjacent sequences: A032092 A032093 A032094 * A032096 A032097 A032098
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KEYWORD
| nonn
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AUTHOR
| Christian G. Bower (bowerc(AT)usa.net)
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