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A073112 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. 0
0, 0, 0, 1, 0, 7, 6, 30, 110, 278, 1332, 3312 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,6
LINKS
Zhi-Wei Sun, On permutations of {1, ..., n} and related topics, arXiv:1811.10503 [math.CO], 2018.
PROG
(PARI) a(n)=sum(k=1, n!, if(frac(sum(i=1, n, 1/(i+component(numtoperm(n, k), i)))), 0, 1))
CROSSREFS
Sequence in context: A341289 A322049 A163260 * A070425 A163842 A328697
KEYWORD
nonn,more
AUTHOR
Benoit Cloitre, Aug 19 2002
EXTENSIONS
More terms from Ryan Propper, Jun 11 2006
STATUS
approved

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Last modified July 17 19:13 EDT 2024. Contains 374377 sequences. (Running on oeis4.)