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Search: id:A073112
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| A073112 |
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Number of permutations p from (1,2,3,...,n) to (1,2,3,...,n) such that 1/(1+p(1) )+1/(2+p(2) )+...+1/(n+p(n) is an integer. |
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+0
1
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| 0, 0, 0, 1, 0, 7, 6, 30, 110, 278, 1332, 3312
(list; graph; listen)
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OFFSET
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1,6
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PROGRAM
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(PARI) a(n)=sum(k=1, n!, if(frac(sum(i=1, n, 1/(i+component(numtoperm(n, k), i)))), 0, 1))
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CROSSREFS
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Sequence in context: A078323 A099255 A163260 this_sequence A070425 A163842 A038272
Adjacent sequences: A073109 A073110 A073111 this_sequence A073113 A073114 A073115
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KEYWORD
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more,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 19 2002
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EXTENSIONS
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More terms from Ryan Propper (rpropper(AT)stanford.edu), Jun 11 2006
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