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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
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
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
KEYWORD
nonn,more
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