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A166027
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a(n) = 6*a(n-2) for n > 2; a(1) = 4, a(2) = 1.
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1
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4, 1, 24, 6, 144, 36, 864, 216, 5184, 1296, 31104, 7776, 186624, 46656, 1119744, 279936, 6718464, 1679616, 40310784, 10077696, 241864704, 60466176, 1451188224, 362797056, 8707129344, 2176782336, 52242776064, 13060694016, 313456656384
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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a(n) = 6^(1/4*(2*n+3+(-1)^n))*(25-23*(-1)^n)/72.
G.f.: x*(4+x)/(1-6*x^2).
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MATHEMATICA
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Join[{4, 1, 24}, LinearRecurrence[{0, 6}, {6, 144}, 25]] (* G. C. Greubel, Apr 21 2016 *)
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PROG
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(Magma) [ n le 2 select 7-3*n else 6*Self(n-2): n in [1..29] ];
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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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STATUS
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approved
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