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Search: id:A083015
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| A083015 |
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a(n) = the number of ordered pairs of n-bit bit strings, such that both bit strings have at least n/2 one-bits, or both have at most n/2 one-bits. |
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+0
1
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| 1, 2, 14, 32, 206, 512, 3128, 8192, 48238, 131072, 750584, 2097152, 11746424, 33554432, 184558304, 536870912, 2908113518, 8589934592, 45923227448, 137438953472, 726419131576, 2199023255552, 11506072128224, 35184372088832
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OFFSET
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0,2
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FORMULA
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a(n) = 4^n/2 + 2^n*c - c^2/2; where c is (n choose n/2) for even n, 0 for odd n.
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EXAMPLE
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a(2)=14 because of the 16 ordered pairs, only (00,11) and (11,00) do not qualify.
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CROSSREFS
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Sequence in context: A093794 A075490 A031301 this_sequence A050591 A073535 A060626
Adjacent sequences: A083012 A083013 A083014 this_sequence A083016 A083017 A083018
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KEYWORD
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nonn
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AUTHOR
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Jon Perry (perry(AT)globalnet.co.uk), May 31 2003
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EXTENSIONS
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Edited by Don Reble (djr(AT)nk.ca), Nov 07 2005
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