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A269019
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a(n) = 2^n + 2*(-1)^n - 1.
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1
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2, -1, 5, 5, 17, 29, 65, 125, 257, 509, 1025, 2045, 4097, 8189, 16385, 32765, 65537, 131069, 262145, 524285, 1048577, 2097149, 4194305, 8388605, 16777217, 33554429, 67108865, 134217725, 268435457, 536870909, 1073741825, 2147483645, 4294967297, 8589934589
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OFFSET
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0,1
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COMMENTS
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Fermat numbers > 3 from A000215 are terms.
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LINKS
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FORMULA
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EXAMPLE
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For n = 6; a(n) = 2^n + 2*(-1)^n - 1 = 2^6 + 2*(-1)^6 - 1 = 65.
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MATHEMATICA
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Table [2^n + 2 (-1)^n - 1, {n, 0, 80}] (* or *) CoefficientList[Series[(2 - 5 x + 5 x^2) / ((1 - 2 x) (1 - x^2)), {x, 0, 33}], x] (* Vincenzo Librandi, Feb 18 2016 *)
LinearRecurrence[{2, 1, -2}, {2, -1, 5}, 40] (* Harvey P. Dale, Feb 25 2022 *)
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PROG
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(Magma) [2^n + 2*(-1)^n - 1: n in [0..300]]
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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