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A027166
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a(n) = Sum_{0<=j<=i<=n} A027157(i, j).
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1
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1, 4, 14, 36, 103, 248, 684, 1624, 4445, 10524, 28762, 68060, 185955, 439984, 1202072, 2844144, 7770361, 18384884, 50228454, 118841812, 324681887, 768205608, 2098776772, 4965759176, 13566706389, 32099171980, 87696568754, 207492309516, 566879531803
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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) = 2*a(n-1)+5*a(n-2)-12*a(n-3)+9*a(n-4)-6*a(n-5)+3*a(n-6) for n>5.
G.f.: (1+x)^2 / ((1-x)^2*(1-6*x^2-3*x^4)).
(End)
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MATHEMATICA
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LinearRecurrence[{2, 5, -12, 9, -6, 3}, {1, 4, 14, 36, 103, 248}, 30] (* Harvey P. Dale, Apr 18 2019 *)
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PROG
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(PARI) Vec((1+x)^2/((1-x)^2*(1-6*x^2-3*x^4)) + O(x^40)) \\ Colin Barker, Feb 20 2016
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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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