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Search: id:A020698
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| A020698 |
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a(n) = 5a(n-1) - 2a(n-2). |
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+0
4
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| 2, 9, 41, 187, 853, 3891, 17749, 80963, 369317, 1684659, 7684661, 35053987, 159900613, 729395091, 3327174229, 15177080963, 69231056357, 315801119859, 1440543486581, 6571115193187, 29974488992773, 136730214577491, 623702094901909, 2845050045354563
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OFFSET
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0,1
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COMMENT
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Coincides with Pisot sequences L(2,9), E(2,9) (at least for first 1000 terms).
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REFERENCES
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S. J. Cyvin and I. Gutman, Kekule structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 78).
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FORMULA
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a(k) = [M^k]_1,3, where M is the 3 by 3 matrix defined as follows: M = [2,1,2;1,1,1;2,1,2]. - Simone Severini (ss54(AT)york.ac.uk), Jun 12 2006
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CROSSREFS
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See A008776 for definitions of Pisot sequences.
Sequence in context: A002825 A052322 A130767 this_sequence A128752 A074611 A152052
Adjacent sequences: A020695 A020696 A020697 this_sequence A020699 A020700 A020701
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KEYWORD
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nonn
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AUTHOR
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David W. Wilson (davidwwilson(AT)comcast.net)
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