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1, 4, 12, 24, 39, 59, 84, 112, 143, 179, 220, 264, 311, 363, 420, 480, 543, 611, 684, 760, 839, 923, 1012, 1104, 1199, 1299, 1404, 1512, 1623, 1739, 1860, 1984, 2111, 2243, 2380, 2520, 2663, 2811, 2964, 3120, 3279, 3443, 3612, 3784, 3959, 4139, 4324, 4512
(list;
graph;
refs;
listen;
history;
text;
internal format)
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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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G.f.: (1 + x + 4*x^2 + 2*x^4 + x^5 - x^6) / ((1 - x)^3*(1 + x^2)).
a(n) = (-1/4-i/4)*((1-i) + (-i)^n - i*i^n) + 2*n + 2*n^2 for n>1, where i=sqrt(-1).
a(n) = 3*a(n-1) - 4*a(n-2) + 4*a(n-3) - 3*a(n-4) + a(n-5) for n>6.
(End)
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PROG
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(PARI) Vec((1 + x + 4*x^2 + 2*x^4 + x^5 - x^6) / ((1 - x)^3*(1 + x^2)) + O(x^50)) \\ Colin Barker, Dec 24 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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EXTENSIONS
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STATUS
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approved
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