A142702 - OEIS

%I #27 Mar 02 2024 01:28:30

%S 5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,

%T 5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8,

%U 5,2,5,8,5,2,5,8,5,2,5,8,5,2,5,8

%N Period 4: repeat [5, 2, 5, 8].

%C From Balmer spectrum of hydrogen.

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (1,-1,1).

%F a(n) = 5+3*cos(n*Pi/2). [From PARI program of Lafont, Aug 30 2009].

%F G.f.: ( 5-3*x+8*x^2 ) / ( (1-x)*(1+x^2) ). - _R. J. Mathar_, Apr 02 2011

%F a(n) = a(n-1) - a(n-2) + a(n-3) for n>3. - _Wesley Ivan Hurt_, Jul 08 2016

%p seq(op([5, 2, 5, 8]), n=1..50); # _Wesley Ivan Hurt_, Jul 08 2016

%t PadRight[{}, 100, {5, 2, 5, 8}] (* _Harvey P. Dale_, Dec 09 2013 *)

%o (PARI) a(n)=5+3*cos(n*Pi/2) \\ [_Jaume Oliver Lafont_, Aug 30 2009]

%o (Magma) &cat [[5, 2, 5, 8]^^30]; // _Wesley Ivan Hurt_, Jul 08 2016

%K nonn,easy

%O 1,1

%A _Paul Curtz_, Sep 23 2008

%E Edited by _N. J. A. Sloane_, Sep 27 2008