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A122088
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Add 10, subtract 5, add 10, subtract 5, ad infinitum.
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1
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1, 11, 6, 16, 11, 21, 16, 26, 21, 31, 26, 36, 31, 41, 36, 46, 41, 51, 46, 56, 51, 61, 56, 66, 61, 71, 66, 76, 71, 81, 76, 86, 81, 91, 86, 96, 91, 101, 96, 106, 101, 111, 106, 116, 111, 121, 116, 126, 121, 131, 126, 136, 131, 141, 136, 146, 141, 151, 146, 156, 151, 161, 156, 166, 161, 171
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OFFSET
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1,2
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COMMENTS
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A brain teaser.
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LINKS
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FORMULA
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G.f.: x*(1+10*x-6*x^2)/((1+x)*(1-x)^2).
a(n) = 9/4+5*n/2+15*(-1)^n/4. (End)
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MAPLE
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MATHEMATICA
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LinearRecurrence[{1, 1, -1}, {1, 11, 6}, 70] (* Harvey P. Dale, Dec 06 2017 *)
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PROG
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(Magma) [9/4 + 5*n/2 + 15*(-1)^n/4 : n in [1..50]]; // Wesley Ivan Hurt, Mar 14 2015
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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Chris H. (chrishale(AT)deotte.com), Oct 17 2006
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EXTENSIONS
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STATUS
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approved
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