A010688 Period 2: repeat (1,7).

1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1, 7, 1

Offset

0,2

Comments

Continued fraction of (7 + sqrt 77)/14. - R. J. Mathar, Nov 21 2011

Links

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

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

Formula

From Paul Barry, May 23 2003: (Start)

a(n) = 4 - 3(-1)^n;

g.f.: (1+7x)/((1+x)(1-x));

e.g.f.: 4*exp(x)-3*exp(-x). (End)

a(n) = 7^n mod 8. - Vincenzo Librandi, Feb 07 2011

Mathematica

PadRight[{}, 120, {1, 7}] (* Harvey P. Dale, Mar 21 2018 *)

Prog

(Sage) [power_mod(7, n, 8)for n in range(0, 92)] # Zerinvary Lajos, Nov 03 2009
(Magma) &cat[[1, 7]^^50]; // Vincenzo Librandi, Feb 07 2011 - Jul 23 2016
(PARI) a(n)=n%2*6+1 \\ Charles R Greathouse IV, Jun 11 2015

Crossrefs

Sequence in context: A296472 A171544 A344698 * A176415 A356948 A363150

Adjacent sequences: A010685 A010686 A010687 * A010689 A010690 A010691

Keyword

nonn,easy

Author

N. J. A. Sloane

Extensions

Formula corrected by Philippe Deléham, Oct 30 2008

Status

approved