%I #19 Dec 26 2023 09:43:33

%S 1,1,2,5,10,10,20,50,100,100,200,500,1000,1000,2000,5000,10000,10000,

%T 20000,50000,100000,100000,200000,500000,1000000,1000000,2000000,

%U 5000000,10000000,10000000,20000000,50000000

%N Numbers covering A000027: a(n) = (1, 1, 2, 5) * A011557(n).

%C 3=1+2, 4=1+1+2, 6=1+5, 7=2+5, 8=1+2+5, 9=1+1+2+5, 11=1+10, 12=2+10, 13=1+2+10.

%C a(n) is used only once. Like weights.

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,10).

%F a(1)=1, a(2)=1, a(3)=2, a(4)=5, a(n)=10*a(n-4). G.f.: x*(1+x+2*x^2+5*x^3)/(1-10*x^4). [Colin Barker, Jan 25 2012]

%t LinearRecurrence[{0,0,0,10},{1,1,2,5},40] (* _Harvey P. Dale_, Jan 21 2019 *)

%o (PARI) a(n)=10^(n\4)*[1/2,1,1,2][n%4+1] \\ _Charles R Greathouse IV_, Dec 21 2011

%K nonn,easy

%O 1,3

%A _Paul Curtz_, Aug 22 2011