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%I #22 Sep 08 2022 08:44:37
%S 0,0,0,0,0,0,1,1,1,2,3,3,4,5,6,7,8,9,10,11,12,14,15,16,18,20,21,23,25,
%T 27,29,31,33,35,37,39,42,44,46,49,52,54,57,60,63,66,69,72,75,78,81,85,
%U 88,91,95,99,102,106,110,114,118,122,126,130,134,138,143,147,151,156,161,165
%N a(n) = floor(n*(n-1)/30).
%H Harvey P. Dale, <a href="/A011883/b011883.txt">Table of n, a(n) for n = 0..1000</a>
%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^6*(x^2 - x + 1)*(x^4 - x^2 + 1)/((1 - x)^3*(1 + x^4 + x^3 + x^2 + x)*(1 + x + x^2)*(1 - x + x^3 - x^4 + x^5 - x^7 + x^8)). (End)
%t Join[{0},Floor[#/15]&/@Accumulate[Range[0,80]]] (* or *) Table[Floor[ (n(n-1))/30],{n,0,80}] (* _Harvey P. Dale_, May 18 2019 *)
%o (Magma) [(n*(n-1)) div 30: n in [0..100]]; // _Vincenzo Librandi_, May 19 2019
%o (PARI) a(n) = (n*(n-1))\30; \\ _Michel Marcus_, May 19 2019
%K nonn,easy
%O 0,10
%A _N. J. A. Sloane_
%E More terms from _Vladimir Joseph Stephan Orlovsky_, Mar 14 2010
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