A010721 - OEIS

%I #24 Dec 14 2023 06:05:44

%S 5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,

%T 10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,5,10,

%U 5,10,5,10,5,10,5,10,5,10,5,10

%N Period 2: repeat (5,10).

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (0,1)

%F a(n) = -5/2*(-1)^n + 15/2. - _Paolo P. Lava_, Oct 27 2006

%F From R. J. Mathar, Oct 20 2008: (Start)

%F a(n) = 5*A000034(n).

%F G.f.: 5(1+2x)/((1-x)(1+x)). (End)

%t Table[5 + 5 Mod[n, 2], {n, 0, 50}] (* _Jinyuan Wang_, Feb 26 2020 *)

%t PadRight[{},80,{5,10}] (* _Harvey P. Dale_, Mar 18 2022 *)

%o (PARI) a(n)=n%2*5+5 \\ _Charles R Greathouse IV_, Jul 13 2016

%Y Cf. A176325.

%K nonn,easy

%O 0,1

%A _N. J. A. Sloane_