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A055990
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a(n) is its own 4th difference.
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6
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1, 4, 14, 50, 181, 657, 2385, 8657, 31422, 114051, 413966, 1502555, 5453761, 19795288, 71850128, 260791401, 946583628, 3435774958, 12470688498, 45264335853, 164294064481, 596331286321, 2164478699633, 7856317702310, 28515747394555, 103502414271126
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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-2 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)/(1-5*x+6*x^2-4*x^3+x^4). [Colin Barker, Apr 05 2012]
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MATHEMATICA
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CoefficientList[Series[(1-x)/(1-5*x+6*x^2-4*x^3+x^4), {x, 0, 30}], x] (* Vincenzo Librandi, Apr 06 2012 *)
LinearRecurrence[{5, -6, 4, -1}, {1, 4, 14, 50}, 30] (* Harvey P. Dale, Oct 18 2015 *)
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PROG
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(Magma) I:=[1, 4, 14, 50]; [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 06 2012
(Maxima)
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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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