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A217675
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Number of permutations in S_n containing an increasing subsequence of length 8.
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3
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1, 65, 2603, 83923, 2410291, 64864819, 1683724308, 42918747000, 1086997811325, 27571922195325, 704311698875426, 18189847735254134, 476311846323448840, 12672229166094171240, 343069245941729668380, 9461927811882316662636, 266091066751920438364275
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OFFSET
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8,2
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LINKS
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FORMULA
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EXAMPLE
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a(8) = 1: 12345678.
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MAPLE
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b:= proc(n) option remember; `if`(n<8, n!, ((-343035+429858*n
+238440*n^3+38958*n^4+634756*n^2+2940*n^5+84*n^6)*b(n-1)
-(1974*n^4+36336*n^3+213240*n^2+407840*n+82425)*(n-1)^2*b(n-2)
+2*(49875+42646*n+6458*n^2)*(n-1)^2*(n-2)^2*b(n-3)
-11025*(n-1)^2*(n-2)^2*(n-3)^2*b(n-4))/ ((n+6)^2*(n+10)^2*(n+12)^2))
end:
a:= n-> n! -b(n):
seq(a(n), n=8..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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