%I #21 Aug 15 2021 05:16:03
%S 0,0,0,0,0,1,2,2,3,4,6,7,8,10,12,14,16,18,20,22,25,28,30,33,36,40,43,
%T 46,50,54,58,62,66,70,74,79,84,88,93,98,104,109,114,120,126,132,138,
%U 144,150,156,163,170,176,183,190,198,205,212,220,228,236,244,252
%N a(n) = floor(n*(n-1)/15).
%H <a href="/index/Rec#order_17">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,0,0,0,0,0,0,0,0,0,0,0,0,1,-2,1).
%F From _R. J. Mathar_, Apr 15 2010: (Start)
%F a(n) = 2*a(n-1) - a(n-2) + a(n-15) - 2*a(n-16) + a(n-17).
%F G.f.: x^5*(1+x^2*(-1+x*(1+x^2*(1+x*(-1+x^2)))))/(1+x*(-2+x*(1+x^13*(-1+(2-x)*x)))). (End)
%t LinearRecurrence[{2, -1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -2, 1}, {0, 0, 0, 0, 0, 1, 2, 2, 3, 4, 6, 7, 8, 10, 12, 14, 16}, 63] (* _Georg Fischer_, Aug 15 2021 *)
%K nonn,easy
%O 0,7
%A _N. J. A. Sloane_.