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A282702
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a(n) = 3*a(n-1) + a(n-2), with a(0)=4, a(1)=11.
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1
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4, 11, 37, 122, 403, 1331, 4396, 14519, 47953, 158378, 523087, 1727639, 5706004, 18845651, 62242957, 205574522, 678966523, 2242474091, 7406388796, 24461640479, 80791310233, 266835571178, 881298023767, 2910729642479, 9613486951204, 31751190496091, 104867058439477, 346352365814522
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = (2^(-n)*((3-sqrt(13))^n*(-5+2*sqrt(13)) + (3+sqrt(13))^n*(5+2*sqrt(13)))) / sqrt(13). - Colin Barker, Feb 26 2017
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MATHEMATICA
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LinearRecurrence[{3, 1}, {4, 11}, 28] (* Indranil Ghosh, Feb 26 2017 *)
RecurrenceTable[{a[0]==4, a[1]==11, a[n]==3 a[n-1] + a[n-2]}, a, {n, 40}] (* or *) CoefficientList[Series[(4 - x)/(1 - 3 x - x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Feb 26 2017 *)
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PROG
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(Magma) I:=[4, 11]; [n le 2 select I[n] else 3*Self(n-1)+Self(n-2): n in [1..40]]; // Vincenzo Librandi, Feb 26 2017
(PARI) Vec((4-x) / (1-3*x-x^2) + O(x^30)) \\ Colin Barker, Feb 26 2017
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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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