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A339226
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Number of oriented series-parallel networks with n elements of 2 colors.
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4
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2, 7, 32, 176, 1066, 6935, 47216, 332700, 2404818, 17734668, 132901644, 1009161505, 7747608480, 60037905076, 468987635982, 3689066578347, 29195587558726, 232303316402615, 1857264782113562, 14912673794505898, 120203145484455930, 972291038495626309
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OFFSET
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1,1
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COMMENTS
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See A339228 for additional details.
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LINKS
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EXAMPLE
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In the following examples elements in series are juxtaposed and elements in parallel are separated by '|'.
a(1) = 2: (1), (2).
a(2) = 7: (11), (12), (21), (22), (1|1), (1|2), (2|2).
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PROG
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seq(n) = {R(n, 2)}
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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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