A346720 a(n) is the number of negative Euler permutations of order 2*n. Bisection (even indices) of A347602.

0, 1, 2, 163, 6724, 692741, 86756038, 16135231015, 3838836369800, 1178853270354697, 447322130002332298, 206783054242756958891, 114117348385587556703692, 74183362210489714472590093, 56080450787901009525514063694, 48790757690364513377740990959151, 48400123863374755985614486072403728

Offset

0,3

Comments

For definitions and comments see A347602.

Links

Table of n, a(n) for n=0..16.

Formula

A346719(n) + a(n) = A000166(2n) (rencontres numbers).

A346719(n) - a(n) = A000364(n) (Euler secant numbers).

a(n) = subfactorial(2*n) / 2 - Im(PolyLog(-2*n, i)).

Maple

# uses A000166.
A346720 := n -> (A000166(2*n) - euler(2*n)) / 2:
seq(A346720(n), n = 0..16);

Mathematica

A346720[n_] := Subfactorial[2 n]/2 - Im[PolyLog[-2 n, I]];
Table[A346720[n], {n, 0, 16}]

Crossrefs

Cf. A347601, A346719, A000166, A000364, A347602.

Sequence in context: A384044 A109420 A162904 * A389389 A259319 A230912

Adjacent sequences: A346717 A346718 A346719 * A346721 A346722 A346723

Keyword

nonn

Author

Peter Luschny, Sep 09 2021

Status

approved