%I #16 Oct 07 2023 05:06:17

%S 10,5,30,10,2,15,70,20,90,1,110,30,130,35,6,40,170,45,190,2,210,55,

%T 230,60,10,65,270,70,290,3,310,80,330,85,14,90,370,95,390,4,410,105,

%U 430,110,18,115,470,120,490,5,510,130,530,135,22,140,570,145,590,6

%N a(n) = lcm(10,n)/gcd(10,n).

%H <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,-1)

%F a(n) = A109051(n) / A109013(n). - _R. J. Mathar_, Feb 12 2019

%F a(n) = 2*a(n-10) - a(n-20). - _R. J. Mathar_, Feb 12 2019

%F Sum_{k=1..n} a(k) ~ (101/40)*n^2. - _Amiram Eldar_, Oct 07 2023

%t Table[LCM[10,n]/GCD[10,n],{n,80}] (* _Harvey P. Dale_, Nov 01 2013 *)

%Y Cf. A070290, A070292, A070293, A109013, A109051.

%K easy,nonn

%O 1,1

%A _Amarnath Murthy_, May 10 2002