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%I #14 Dec 12 2023 08:31:51
%S 1,5,9,7,7,9,5,1,3,3,1,5,9,7,7,9,5,1,3,3,1,5,9,7,7,9,5,1,3,3,1,5,9,7,
%T 7,9,5,1,3,3,1,5,9,7,7,9,5,1,3,3,1,5,9,7,7,9,5,1,3,3,1,5,9,7,7,9,5,1,
%U 3,3,1,5,9,7,7,9,5,1,3,3,1,5,9,7,7,9,5,1,3,3,1,5,9,7,7,9,5,1,3,3,1,5,9,7,7
%N Period 10: 1, 5, 9, 7, 7, 9, 5, 1, 3, 3 repeated.
%C The last digit of A108981(n).
%C Also the continued fraction of (290003+sqrt(240183699293))/652402.
%C Also the decimal expansion of 13073/81819.
%C The period contains each of the 5 odd digits twice.
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (2,-2,2,-2,1).
%F a(n)+a(n+5) = 10 = A010692(n).
%F a(n) = a(n+10) .
%F a(10*k+9+i) = a(10*k+18-i) (palindromic).
%F a(n) = 2*a(n-1)-2*a(n-2)+2*a(n-3)-2*a(n-4)+a(n-5). G.f.: -(1+3*x+x^2-3*x^3+3*x^4)/ ((x-1) * (x^4-x^3+x^2-x+1)).
%t PadRight[{},120,{1,5,9,7,7,9,5,1,3,3}] (* _Harvey P. Dale_, Apr 23 2020 *)
%o (PARI) 13073/81819. \\ _Charles R Greathouse IV_, Jul 21 2015
%K nonn,easy
%O 0,2
%A _Paul Curtz_, Jul 12 2008
%E Edited by _R. J. Mathar_, Sep 07 2009
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