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A007455
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Number of subsequences of [ 1,...,n ] in which each odd number has an even neighbor.
(Formerly M2480)
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4
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1, 1, 3, 5, 11, 17, 39, 61, 139, 217, 495, 773, 1763, 2753, 6279, 9805, 22363, 34921, 79647, 124373, 283667, 442961, 1010295, 1577629, 3598219, 5618809, 12815247, 20011685, 45642179, 71272673, 162557031, 253841389, 578955451, 904069513
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| G.f. = (-1-x-2 x^3)/(-1+3 x^2+2 x^4) (* From Harvey P. Dale, Feb 18 2011 *)
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REFERENCES
| R. K. Guy, Moser, William O.J.: Numbers of subsequences without isolated odd members. Fibonacci Quarterly, 34, No. 2, 152-155 (1996).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| T. D. Noe, Table of n, a(n) for n=0..400
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FORMULA
| a(n) = 3*a(n-2) + 2*a(n-4).
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MATHEMATICA
| CoefficientList[Series[(-1-x-2 x^3)/(-1+3 x^2+2 x^4), {x, 0, 40}], x] (* From Harvey P. Dale, Feb 18 2011 *)
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CROSSREFS
| Cf. A007481, A007482, A007484.
Sequence in context: A060647 A155989 A125557 * A034729 A115786 A128550
Adjacent sequences: A007452 A007453 A007454 * A007456 A007457 A007458
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KEYWORD
| nonn,easy,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein
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