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A010688 Period 2: repeat (1,7).

%I A010688 #48 Dec 18 2023 09:37:01
%S A010688 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,
%T A010688 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,
%U A010688 1,7,1,7,1,7,1,7,1,7,1,7,1
%N A010688 Period 2: repeat (1,7).
%C A010688 Continued fraction of (7 + sqrt 77)/14. - _R. J. Mathar_, Nov 21 2011
%H A010688 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1).
%F A010688 From _Paul Barry_, May 23 2003: (Start)
%F A010688 a(n) = 4 - 3(-1)^n;
%F A010688 g.f.: (1+7x)/((1+x)(1-x));
%F A010688 e.g.f.: 4*exp(x)-3*exp(-x). (End)
%F A010688 a(n) = 7^n mod 8. - _Vincenzo Librandi_, Feb 07 2011
%t A010688 PadRight[{},120,{1,7}] (* _Harvey P. Dale_, Mar 21 2018 *)
%o A010688 (Sage) [power_mod(7,n,8)for n in range(0,92)] # _Zerinvary Lajos_, Nov 03 2009
%o A010688 (Magma) &cat[[1, 7]^^50]; // _Vincenzo Librandi_, Feb 07 2011 - Jul 23 2016
%o A010688 (PARI) a(n)=n%2*6+1 \\ _Charles R Greathouse IV_, Jun 11 2015
%K A010688 nonn,easy
%O A010688 0,2
%A A010688 _N. J. A. Sloane_
%E A010688 Formula corrected by _Philippe Deléham_, Oct 30 2008