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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
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0, 0, 0, 1, 0, 7, 6, 30, 110, 278, 1332, 3312
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,6
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PROG
| (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
| Sequence in context: A099255 A198460 A163260 * A070425 A163842 A038272
Adjacent sequences: A073109 A073110 A073111 * A073113 A073114 A073115
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KEYWORD
| more,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 19 2002
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EXTENSIONS
| More terms from Ryan Propper (rpropper(AT)stanford.edu), Jun 11 2006
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