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A264463
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Number of permutations of [n] with exactly four (possibly overlapping) occurrences of the generalized pattern 23-1.
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2
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3, 62, 624, 5513, 46880, 396545, 3388893, 29497132, 262619041, 2397130075, 22458202716, 216063700398, 2134707078315, 21655074753266, 225471830153938, 2408463527492433, 26380434283682048, 296130434080550183, 3404883834560222589, 40077202708717399396
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OFFSET
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5,1
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LINKS
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EXAMPLE
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a(5) = 3: 34512, 34521, 45231.
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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, 5), polynom), j=1..o))
end:
a:= n-> coeff(b(n, 0), x, 4):
seq(a(n), n=5..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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