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Search: id:A124188
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| A124188 |
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A permutation of the integers {1,2,....,n} is k-good if each of the k! patterns on k integers is contained as a subsequence of the permutation. For example, with k=2, there are n!-2 permutations that contain both a "12" and a "21" pattern. Sequence lists the number of 3-good permutations on {1,2,...,n}, i.e. permutations that contain each of the six patterns {123,132,213,231,312,321}. |
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1
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OFFSET
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1,5
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FORMULA
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For n >= 5, a(n)= n! - (6{2n choose n}/(n+1)) + 10(2^{n-1}) + 4{n choose 2} - 14n - 2F_{n+1} + 20, where F_n is the Fibonacci sequence
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CROSSREFS
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Sequence in context: A078280 A125058 A101393 this_sequence A078276 A117076 A037057
Adjacent sequences: A124185 A124186 A124187 this_sequence A124189 A124190 A124191
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KEYWORD
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nonn
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AUTHOR
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Nicole Holder, David Simpson and Anant Godbole (tertsu(AT)gmail.com), Dec 06 2006
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