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A264468
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Number of permutations of [n] with exactly nine (possibly overlapping) occurrences of the generalized pattern 23-1.
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2
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18, 780, 15627, 235045, 3086010, 37816568, 449766437, 5291113080, 62237008779, 736806459069, 8816027319934, 106900514193980, 1315953951437664, 16464756848575162, 209528329365176670, 2713295547732215190, 35762229764646245816, 479809424452611001696
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OFFSET
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7,1
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LINKS
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EXAMPLE
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a(7) = 18: 3567241, 4567123, 4567132, 4567213, 4567312, 4567321, 4672351, 4673512, 4673521, 5671342, 5672314, 5672413, 5672431, 5673241, 5674231, 6734512, 6734521, 6745231.
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MAPLE
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b:= proc(u, o) option remember; `if`(u+o=0, 1, add(
b(u-j, o+j-1), j=1..u) +add(convert(series(
b(u+j-1, o-j)*x^u, x, 10), polynom), j=1..o))
end:
a:= n-> coeff(b(n, 0), x, 9):
seq(a(n), n=7..25);
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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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