A346719 a(n) is the number of positive Euler permutations of order 2*n. Bisection (even indices) of A347601.

1, 0, 7, 102, 8109, 642220, 89458803, 15935870034, 3858227881945, 1176448390679256, 447692501190569823, 206713705368363820990, 114132862919751113790597, 74179275137980421348697732, 56081703047542413155379531979, 48790316146471264354636437276330, 48400301382766335524903922737193393

Offset: 0

Author

Peter Luschny, Sep 09 2021

Keywords

• nonn

Comments

For definitions and comments see A347601.

Crossrefs

Cf. A347601, A346720, A000166, A000364, A347602.

Programs

Maple

A346719 := n -> (A000166(2*n) + euler(2*n)) / 2:
seq(A346719(n), n = 0..16);

Mathematica

A346719[n_] := Subfactorial[2 n]/2 + Im[PolyLog[-2 n, I]];
Table[A346719[n], {n, 0, 16}]

Formula

a(n) + A346720(n) = A000166(2n) (rencontres numbers).

a(n) - A346720(n) = A000364(n) (Euler secant numbers).

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