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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
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| 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
| a(2)=14 because of the 16 ordered pairs, only (00,11) and (11,00) do not qualify.
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CROSSREFS
| Sequence in context: A075490 A031301 A202638 * A050591 A073535 A060626
Adjacent sequences: A083012 A083013 A083014 * A083016 A083017 A083018
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KEYWORD
| nonn
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AUTHOR
| Jon Perry (perry(AT)globalnet.co.uk), May 31 2003
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EXTENSIONS
| Edited by Don Reble (djr(AT)nk.ca), Nov 07 2005
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