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0, 1, 1, 3, 3, 11, 9, 35, 33, 105, 105, 339, 313, 1035, 1017, 3115, 3099, 9579, 9345, 28947, 28713, 86979, 86825, 263187, 260865, 791577, 789497, 2376555, 2374521, 7150443, 7129401, 21471315, 21450489, 64431843, 64413177, 193487947, 193292811, 580650075
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,4
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LINKS
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FORMULA
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a(n) ~ 3^(n/2) / 2 if n is even and a(n) ~ 3^((n+1)/2) / 2 if n is odd.
a(n) ~ (1+sqrt(3) + (-1)^n*(1-sqrt(3))) * 3^(n/2) / 4.
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MATHEMATICA
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nmax = 60; 3^Range[0, nmax] - CoefficientList[Series[Product[(1 - x^k)/(1 - 3*x^k), {k, 1, nmax}], {x, 0, nmax}], x]
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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