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A010705 Period 2: repeat (3,7).

%I A010705 #40 Feb 21 2024 01:44:19
%S A010705 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,
%T A010705 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,
%U A010705 3,7,3,7,3,7,3,7,3,7,3,7,3
%N A010705 Period 2: repeat (3,7).
%C A010705 Continued fraction expansion of (21 + 5*sqrt(21))/14 (decimal expansion is given by A176106). - _R. J. Mathar_, Mar 08 2012
%C A010705 If an initial 2 is prepended to this sequence, it is Sylvester's sequence (A000058) modulo 10. - _Alonso del Arte_, Mar 25 2015
%C A010705 Also, smallest prime factor of 8^n-1 for n >= 1. - _Sean A. Irvine_, Oct 15 2023
%H A010705 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).
%F A010705 G.f.: (3+7x)/((1-x)(1+x)). - _R. J. Mathar_, Nov 21 2011
%t A010705 Table[Mod[30n - 15 + 2(-1)^n, 10], {n, 100}] (* _Alonso del Arte_, Mar 25 2015 *)
%t A010705 PadRight[{},120,{3,7}] (* _Harvey P. Dale_, Jan 14 2019 *)
%o A010705 (PARI) a(n)=3+n%2*4 \\ _Charles R Greathouse IV_, Dec 21 2011
%o A010705 (Python)
%o A010705 def A010705(n): return 3|((n&1)<<2) # _Chai Wah Wu_, Aug 12 2023
%K A010705 nonn,easy
%O A010705 0,1
%A A010705 _N. J. A. Sloane_