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Search: id:A065497
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| A065497 |
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Number of (binary) bit strings of length n having at least one even length block of 0's followed by an even length block of 1's. |
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+0
4
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| 1, 2, 7, 16, 40, 92, 209, 468, 1027, 2242, 4832, 10360, 22049, 46694, 98419, 206588, 432132, 900980, 1873297, 3884904, 8038295, 16597478, 34205700, 70372728, 144550977, 296486538, 607301551, 1242406568, 2538762208, 5182207180
(list; graph; listen)
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OFFSET
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4,2
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FORMULA
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G.f.: x^4/[(2x-1)(1-3x^2-2x^3+x^4)]
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EXAMPLE
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a(6)=7 because of 000011, 001100, 001101, 001111, 010011, 100110, 110011
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CROSSREFS
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Cf. A065455, A065494, A065495.
Sequence in context: A041887 A129441 A093971 this_sequence A131727 A073371 A113224
Adjacent sequences: A065494 A065495 A065496 this_sequence A065498 A065499 A065500
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KEYWORD
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nonn
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AUTHOR
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Len Smiley (smiley(AT)math.uaa.alaska.edu), Nov 24 2001
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