|
%I #20 Feb 24 2023 11:37:49
%S 0,0,0,0,0,0,1,2,2,3,4,5,6,7,8,10,11,12,14,16,18,20,22,24,26,28,30,33,
%T 36,38,41,44,47,50,53,56,60,63,66,70,74,78,82,86,90,94,98,102,107,112,
%U 116,121,126,131,136,141,146,152,157,162,168
%N a(n) = floor(n*(n-1)/21).
%H <a href="/index/Rec#order_23">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,-2,1).
%F G.f.: x^6*(1-x^2+x^3+x^9-x^10+x^12)/((1-x)^2*(1-x^21)). - _R. J. Mathar_, Sep 09 2008
%F a(n) = 2*a(n-1) - a(n-2) + a(n-21) - 2*a(n-22) + a(n-23). - _R. J. Mathar_, Aug 11 2021
%t CoefficientList[Series[x^6*(1-x^2+x^3+x^9-x^10+x^12) / ((1-x)^2*(1-x^21)), {x, 0, 64}], x] (* _Georg Fischer_, Aug 15 2021 *)
%t LinearRecurrence[{2,-1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,-2,1},{0,0,0,0,0,0,1,2,2,3,4,5,6,7,8,10,11,12,14,16,18,20,22},70] (* _Harvey P. Dale_, Feb 24 2023 *)
%K nonn,easy
%O 0,8
%A _N. J. A. Sloane_
|
