%I #18 Dec 12 2023 09:41:02
%S 0,2,6,2,0,0,2,6,2,0,0,2,6,2,0,0,2,6,2,0,0,2,6,2,0,0,2,6,2,0,0,2,6,2,
%T 0,0,2,6,2,0,0,2,6,2,0,0,2,6,2,0,0,2,6,2,0,0,2,6,2,0,0,2,6,2,0
%N Periodic sequence (0, 2, 6, 2, 0).
%C Also: twice the partial sums of A117444. - _R. J. Mathar_, Feb 01 2008
%H Rozsa Peter, Leon Harkleroad, <a href="https://doi.org/10.1007/BF03023987">Mathematics is Beautiful</a>, Math. Intellig., 12 (No. 1, 1990), 58-64.
%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) = n(n+1) mod 10
%F O.g.f.: -2/(x-1)+(2*x^3+2*x^2-2*x-2)/(1+x+x^2+x^3+x^4). a(n)=a(n-5). - _R. J. Mathar_, Feb 01 2008
%t PadRight[{},70,{0,2,6,2,0}] (* _Harvey P. Dale_, Mar 22 2012 *)
%o (PARI) a(n)=[0, 2, 6, 2, 0][n%5+1] \\ _Charles R Greathouse IV_, Jul 13 2016
%K nonn,easy
%O 0,2
%A _Franz Vrabec_, Jan 30 2008