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A065495
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Number of (binary) bit strings of length n in which an odd length block of 0's is followed by an odd length block of 1's.
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3
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1, 2, 6, 14, 32, 72, 156, 336, 712, 1496, 3120, 6464, 13328, 27360, 55968, 114144, 232192, 471296, 954816, 1931264, 3900800, 7869312, 15858432, 31928832, 64232704, 129128960, 259431936, 520941056, 1045557248, 2097616896
(list; graph; refs; listen; history; internal format)
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OFFSET
| 2,2
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (2,2,-2,-4).
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FORMULA
| G.f.: x^2/[(1-2x)(1-2x^2-2x^3)]
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EXAMPLE
| a(4)=6 because of 0100,0101,1010,1101,0111,0001
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CROSSREFS
| Cf. A061279 [=2^n - a(n)], A065455, A065494, A065497.
Sequence in context: A035592 A096238 A074878 * A131352 A051485 A077999
Adjacent sequences: A065492 A065493 A065494 * A065496 A065497 A065498
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KEYWORD
| nonn
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AUTHOR
| Len Smiley (smiley(AT)math.uaa.alaska.edu), Nov 24 2001
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