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Search: id:A032087
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| A032087 |
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Number of reversible strings with n beads of 4 colors. If more than 1 bead, not palindromic. |
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+0
2
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| 4, 6, 24, 120, 480, 2016, 8064, 32640, 130560, 523776, 2095104, 8386560, 33546240, 134209536, 536838144, 2147450880, 8589803520, 34359607296, 137438429184, 549755289600, 2199021158400, 8796090925056
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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C. G. Bower, Transforms (2)
Elizabeth Wilmer, Notes on Stephan's conjectures 72, 73, and 74
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FORMULA
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"BHK" (reversible, identity, unlabeled) transform of 4, 0, 0, 0...
a(2n+1) = 2^(4n+1) - 2^(2n+1), a(2n) = 2^(4n-1) - 2^(2n) + 2^(2n-1), a(1)=4.
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CROSSREFS
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Cf. A088037.
Sequence in context: A067001 A057343 A000287 this_sequence A136591 A009459 A123055
Adjacent sequences: A032084 A032085 A032086 this_sequence A032088 A032089 A032090
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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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