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A003109 a(n) = number of special even permutations of 2*n+1.
(Formerly M5045)
3
1, 1, 17, 117, 1413, 46389, 1211085, 47977305, 2302999889, 137682614769, 9844042388505, 832087399629125 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) is the number of even permutations, pi(0),...,pi(2*n), of 0,...,2*n such that pi(0) = 0 and p(k) = k + pi(k) (mod 2*n+1), k=0,...,2*n is also a permutation of 0,...,2*n. - Sean A. Irvine, Jan 30 2015

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..12.

D. H. Lehmer, Some properties of circulants, J. Number Theory 5 (1973), 43-54.

CROSSREFS

Cf. A003110 (special odd permutations), A003111 (total).

Sequence in context: A086020 A056117 A196575 * A066607 A083200 A102353

Adjacent sequences:  A003106 A003107 A003108 * A003110 A003111 A003112

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane

EXTENSIONS

a(8)-a(9) from Sean A. Irvine, Jan 31 2015

a(10)-a(12) from Vaclav Kotesovec, May 17 2019 (using the terms of A003111 and A003112)

STATUS

approved

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Last modified January 18 09:26 EST 2022. Contains 350454 sequences. (Running on oeis4.)