A131806 Period 4: repeat [0, 2, 4, 6].

0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6, 0, 2, 4, 6

Offset

1,2

Links

Table of n, a(n) for n=1..108.

Salvatore Gambino, Terne pitagoriche primitive

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

Formula

a(n) = 3+(-1)^n+2*(-1)^((2*n+1-(-1)^n)/4).

G.f.: 2*x^2*(1+2*x+3*x^2)/((1-x)*(1+x)*(1+x^2)). a(n) = 2*A010873(n-1). - R. J. Mathar, Jan 15 2008

From Wesley Ivan Hurt, Jul 09 2016: (Start)

a(n) = a(n-4) for n>4.

a(n) = 3 + cos(n*Pi) + 2*cos(n*Pi/2) - 2*sin(n*Pi/2) + I*sin(n*Pi). (End)

Maple

seq(op([0, 2, 4, 6]), n=1..40); # Wesley Ivan Hurt, Jul 09 2016

Mathematica

PadRight[{}, 100, {0, 2, 4, 6}] (* Wesley Ivan Hurt, Jul 09 2016 *)

Prog

(Magma) &cat [[0, 2, 4, 6]^^30]; // Wesley Ivan Hurt, Jul 09 2016

Crossrefs

Cf. A010873.

Sequence in context: A128124 A182687 A141062 * A004518 A013670 A121206

Adjacent sequences: A131803 A131804 A131805 * A131807 A131808 A131809

Keyword

nonn,easy

Author

Salvatore Gambino (salvatore.gambino(AT)fastwebnet.it), Oct 04 2007

Extensions

More terms from R. J. Mathar, Jan 15 2008

Status

approved