A010705 Period 2: repeat (3,7).

3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3, 7, 3

Offset

0,1

Comments

Continued fraction expansion of (21 + 5*sqrt(21))/14 (decimal expansion is given by A176106). - R. J. Mathar, Mar 08 2012

If an initial 2 is prepended to this sequence, it is Sylvester's sequence (A000058) modulo 10. - Alonso del Arte, Mar 25 2015

Also, smallest prime factor of 8^n-1 for n >= 1. - Sean A. Irvine, Oct 15 2023

Links

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

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

Formula

G.f.: (3+7x)/((1-x)(1+x)). - R. J. Mathar, Nov 21 2011

Mathematica

Table[Mod[30n - 15 + 2(-1)^n, 10], {n, 100}] (* Alonso del Arte, Mar 25 2015 *)
PadRight[{}, 120, {3, 7}] (* Harvey P. Dale, Jan 14 2019 *)

Prog

(PARI) a(n)=3+n%2*4 \\ Charles R Greathouse IV, Dec 21 2011
(Python)
def A010705(n): return 3|((n&1)<<2) # Chai Wah Wu, Aug 12 2023

Crossrefs

Sequence in context: A329341 A244191 A161973 * A244189 A200481 A016665

Adjacent sequences: A010702 A010703 A010704 * A010706 A010707 A010708

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved