A326483 a(n) = 2^n*E2_{n}(1/2) with E2_{n} the polynomials defined in A326480.

1, -2, -4, 40, 80, -1952, -3904, 177280, 354560, -25866752, -51733504, 5535262720, 11070525440, -1633165156352, -3266330312704, 635421069967360, 1270842139934720, -315212388819402752, -630424777638805504, 194181169538675507200

Offset: 0

Author

Peter Luschny, Jul 12 2019

Keywords

• sign

Comments

For comments see A326480.

Crossrefs

Bisections (up to signs): A002436 (even), A000816 (odd).

Cf. A326480, A155585, A326481, A326482, A326483, A326484.

Programs

Maple

# The function E2(n) is defined in A326480.
seq(subs(x=1/2, 2^n*E2(n)), n=0..22);

Formula

From Emanuele Munarini, Aug 22 2022: (Start)

E.g.f. for the sequence of the absolute values: (1+tan(2*t))/cos(2*t).

|a(2*n)| = 2^(2*n) |E(2*n)|.

|a(2*n+1)| = 2^(2*n+1) Sum_{k=0..n} binomial(2*n+1,2*k) |E(2*k)| T(n-k+1), where the E(n) are the Euler numbers (A122045) and the T(n) are the tangent numbers (A000182). (End)