A010675 Period 2: repeat (0,4).

0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0, 4, 0

Offset

0,2

Comments

Decimal expansion of 4/99. - Elmo R. Oliveira, Sep 28 2025

Links

Table of n, a(n) for n=0..80.

Index entries for linear recurrences with constant coefficients, signature (0,1).

Formula

a(n) = 2*(1 - (-1)^n) = 4*(n mod 2). - Paolo P. Lava, Oct 20 2006

O.g.f.: -2/(1+x) - 2/(x-1). - R. J. Mathar, Feb 19 2008

From Wesley Ivan Hurt, May 21 2013: (Start)

a(n) = 4*(1 + floor((n+1)/2) - ceiling((n+1)/2)).

a(n) = 4*cos(Pi*(n+1)/2)^2. (End)

From Elmo R. Oliveira, Sep 28 2025: (Start)

E.g.f.: 4*sinh(x).

a(n) = A010673(n)^2. (End)

Mathematica

PadRight[{}, 120, {0, 4}] (* Harvey P. Dale, Feb 11 2025 *)

Prog

(Magma) &cat [[0, 4]^^50]; // Bruno Berselli, Dec 10 2015
(PARI) a(n)=n%2*4 \\ Charles R Greathouse IV, Jul 23 2016

Crossrefs

Cf. A000035, A010673.

Sequence in context: A391753 A019920 A246130 * A035673 A035638 A347156

Adjacent sequences: A010672 A010673 A010674 * A010676 A010677 A010678

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved