A010694 Period 2: repeat (2,4).

2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2

Offset

0,1

Comments

Simple continued fraction expansion of 1 + sqrt(3/2) = A176051. - R. J. Mathar, Mar 08 2012

Number of linear characters of dihedral group of order 2(n+1). - Eric M. Schmidt, Feb 12 2013

a(n) is the n-th increment between two consecutive elements of the wheel in the wheel factorization with the basis {2, 3}. See A038179. - Wojciech Raszka, May 10 2019

In base 3, make a sequence such that after the initial term 2, each term is the sum of the squares of the digits of the previous term. That's this sequence (see A000216 for the base 10 version). - Alonso del Arte, Mar 19 2020

Links

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

INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1073

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

Formula

From R. J. Mathar, Aug 28 2008: (Start)

a(n) = 2 * A000034(n).

G.f.: 2(1 + 2x)/((1 - x)(1 + x)). (End)

a(n) = a(n-2) for n >= 2. - Jaume Oliver Lafont, Mar 20 2009

a(n) = 2^(n+1) mod 6. - Roderick MacPhee, Mar 31 2011

Mathematica

ContinuedFraction[1 + Sqrt[6]/2, 100] (* Alonso del Arte, Mar 25 2020 *)

Prog

(PARI) a(n)=2*(1+n%2) \\ Jaume Oliver Lafont, Mar 20 2009
(Scala) (0 to 99).map(_ % 2 * 2 + 2) // Alonso del Arte, Mar 25 2020

Crossrefs

Cf. A000034, A038179, A176051.

Sequence in context: A308658 A158137 A336409 * A111737 A056672 A037201

Adjacent sequences: A010691 A010692 A010693 * A010695 A010696 A010697

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved