A003109 a(n) = number of special even permutations of 2*n+1.

1, 1, 17, 117, 1413, 46389, 1211085, 47977305, 2302999889, 137682614769, 9844042388505, 832087399629125

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• more

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).

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)