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Search: id:A032085
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| A032085 |
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Number of reversible strings with n beads of 2 colors. If more than 1 bead, not palindromic. |
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+0
4
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| 2, 1, 2, 6, 12, 28, 56, 120, 240, 496, 992, 2016, 4032, 8128, 16256, 32640, 65280, 130816, 261632, 523776, 1047552, 2096128, 4192256, 8386560, 16773120, 33550336, 67100672, 134209536, 268419072, 536854528
(list; graph; listen)
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OFFSET
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1,1
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REFERENCES
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S. J. Cyvin et al., Theory of polypentagons, J. Chem. Inf. Comput. Sci., 33 (1993), 466-474.
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LINKS
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C. G. Bower, Transforms (2)
INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1022
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FORMULA
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"BHK" (reversible, identity, unlabeled) transform of 2, 0, 0, 0...
a(n) = 2^(n-1)-2^floor((n-1)/2), n > 1. - Vladeta Jovovic (vladeta(AT)Eunet.yu), Nov 11 2001
For n>1 g.f. = 1/((1-2*x)*(1-2*x^2)) - Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 25 2004
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CROSSREFS
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Cf. A005418. Essentially the same as A122746.
Row sums of triangle A034877.
Sequence in context: A020825 A110422 A131804 this_sequence A032163 A038078 A000139
Adjacent sequences: A032082 A032083 A032084 this_sequence A032086 A032087 A032088
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KEYWORD
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nonn
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AUTHOR
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Christian G. Bower (bowerc(AT)usa.net)
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