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4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (0,0,0,1)
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FORMULA
| a(n) = 1 + [2|n] + 2*[4|n] = 2 + (-1)^n + cos(n*Pi/2), where [x|y] = 1 when x divides y, 0 otherwise.
a(n) = a(n-4).
Multiplicative with a(p^e) = GCD(p^e, 4). David W. Wilson (davidwwilson(AT)comcast.net) Jun 12, 2005.
Dirichlet g.f. (1+1/2^s+2/4^s)*zeta(s). - R. J. Mathar, Feb 28 2011
G.f. ( -4-x-2*x^2-x^3 ) / ( (x-1)*(1+x)*(1+x^2) ). - R. J. Mathar, Apr 04 2011
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CROSSREFS
| Cf. A109004.
Sequence in context: A087230 A030787 A176218 * A187025 A074695 A069098
Adjacent sequences: A109005 A109006 A109007 * A109009 A109010 A109011
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KEYWORD
| nonn,easy,mult
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AUTHOR
| Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu)
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