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Search: id:A082972
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| A082972 |
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Number of permutations of length n containing 4 occurrences of 132. |
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+0
1
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| 82, 410, 1918, 8657, 38225, 166322, 716170, 3059864, 12994936, 54924212, 231235054, 970347575, 4060697955, 16952812170, 70629116910, 293720506860, 1219498444500, 5055891511980, 20933654593020, 86571545598642
(list; graph; listen)
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OFFSET
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6,1
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LINKS
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T. Mansour and A. Vainshtein, Counting occurrences of 132 in a permutation
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FORMULA
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a(n)=(2*n-12)!/n!/24/(n-6)!*(n^9+102*n^8-282*n^7-12264*n^6+32589*n^5+891978*n^4-7589428*n^3+25452024*n^2-39821760*n+23950080)
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PROGRAM
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(PARI) a(n)=(2*n-12)!/n!/24/(n-6)!*(n^9+102*n^8-282*n^7-12264*n^6+32589*n^5+891978*n^4-\ 7589428*n^3+25452024*n^2-39821760*n+23950080)
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CROSSREFS
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Cf. A002054 (number of permutations of length n containing 1 occurrence of 132).
Sequence in context: A102956 A031696 A005972 this_sequence A031422 A002309 A128959
Adjacent sequences: A082969 A082970 A082971 this_sequence A082973 A082974 A082975
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), May 27 2003
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