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

Author

N. J. A. Sloane

Keywords

• nonn
• easy

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

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

Programs

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 *)

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

Formula

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