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

Author

N. J. A. Sloane

Keywords

• nonn
• easy

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

• INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 1073
• Index entries for linear recurrences with constant coefficients, signature (0,1).

Crossrefs

Cf. A000034, A038179, A176051.

Programs

Mathematica

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

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

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