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A055989
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a(n) is its own 4th difference.
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4
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1, 3, 10, 36, 131, 476, 1728, 6272, 22765, 82629, 299915, 1088589, 3951206, 14341527, 52054840, 188941273, 685792227, 2489191330, 9034913540, 32793647355, 119029728628, 432037221840, 1568147413312, 5691839002677, 20659429692245, 74986666876571, 272175964826781
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OFFSET
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1,2
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COMMENTS
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Number of compositions of 4*n-3 into parts 1 and 4. - Seiichi Manyama, Feb 03 2024
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LINKS
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FORMULA
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G.f.: x*(1-x)^2/(1 - 5*x + 6*x^2 - 4*x^3 + x^4). - Colin Barker Apr 04 2012
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MATHEMATICA
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CoefficientList[Series[(1-x)^2/(1-5*x+6*x^2-4*x^3+x^4), {x, 0, 40}], x] (* Vincenzo Librandi, Apr 05 2012 *)
LinearRecurrence[{5, -6, 4, -1}, {1, 3, 10, 36}, 30] (* Harvey P. Dale, Jan 10 2014 *)
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PROG
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(Magma) I:=[1, 3, 10, 36]; [n le 4 select I[n] else 5*Self(n-1)-6*Self(n-2)+4*Self(n-3)-Self(n-4): n in [1..30]]; // Vincenzo Librandi, Apr 05 2012
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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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EXTENSIONS
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STATUS
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approved
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