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%I #50 Feb 24 2024 01:09:48
%S 9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,
%T 1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,
%U 3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1,9,7,5,3,1
%N Period 5: repeat [9, 7, 5, 3, 1].
%C Decimal expansion of 9 + 1/2 + 1/4 + 1/313 + 1/378244 + 1/2959729702407 = 975310/99999. - _Bruno Berselli_, Oct 02 2018
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,1).
%F a(n) = 1 + 2*(-n mod 5). [From Wilson Mathematica program (2004)]
%F a(n) = 9 - (2*(n-1) mod 10). [From Greathouse PARI program (2014)]
%F From _Robert Israel_, Jul 16 2015: (Start)
%F G.f.: (9 + 7*x + 5*x^2 + 3*x^3 + x^4)/(1 - x^5).
%F a(n) = a(n-5).
%F a(n) + a((a(n)+1)/2) = 10. (End)
%p map(op,[[9,7,5,3,1]$20]); # _Robert Israel_, Jul 16 2015
%t Table[2 Mod[-n, 5] + 1, {n, 105}] (* _Robert G. Wilson v_, Jul 31 2004 *)
%t PadRight[{}, 120, {9, 7, 5, 3, 1}] (* _Harvey P. Dale_, Dec 19 2012 *)
%o (PARI) a(n) = 9 - 2*(n-1)%10; \\ _Charles R Greathouse IV_, Aug 25 2014
%o (Magma) &cat [[9, 7, 5, 3, 1]: n in [0..20]]; // _Vincenzo Librandi_, Jul 16 2015
%K nonn,easy
%O 1,1
%A _Odimar Fabeny_, Jul 29 2004
%E Edited by _N. J. A. Sloane_ and _Robert G. Wilson v_, Jul 31 2004
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