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A147688
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a(n) = ((6 + sqrt(8))^n + (6 - sqrt(8))^n)/2.
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0
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1, 6, 44, 360, 3088, 26976, 237248, 2091648, 18456832, 162915840, 1438198784, 12696741888, 112091336704, 989587267584, 8736489783296, 77129433907200, 680931492954112, 6011553766047744, 53072563389857792, 468547255228956672
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = 12*a(n-1) - 28*a(n-2), a(0)=1, a(1)=6.
G.f.: (1-6x)/(1-12x+28x^2).
a(n) = (Sum_{k=0..n} A098158(n,k)*6^(2k)*8^(n-k))/6^n.
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MATHEMATICA
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LinearRecurrence[{12, -28}, {1, 6}, 30] (* Harvey P. Dale, Apr 23 2011 *)
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PROG
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(Magma) Z<x>:= PolynomialRing(Integers()); N<r8>:=NumberField(x^2-8); S:=[ ((6+r8)^n+(6-r8)^n)/2: n in [0..19] ]; [ Integers()!S[j]: j in [1..#S] ]; // Klaus Brockhaus, Nov 13 2008
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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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Al Hakanson (hawkuu(AT)gmail.com), Nov 10 2008
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EXTENSIONS
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STATUS
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approved
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