%I #14 Jul 30 2015 14:53:57
%S 0,0,0,0,0,1,1,2,2,3,4,5,6,8,9,11,12,14,16,18,20,22,24,26,29,31,34,36,
%T 39,42,45,48,52,55,59,62,66,70,74,78,82,86,90,95,99,104,108,113,118,
%U 123,128,134,139,145,150,156,162,168,174,180,186,192,199,205,212,218,225,232
%N [ n(n-1)/19 ].
%H <a href="/index/Rec#order_21">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, 1, -2, 1).
%F a(n) = +2*a(n-1) -a(n-2) +a(n-19) -2*a(n-20) +a(n-21). [From _R. J. Mathar_, Apr 15 2010]
%F G.f.: -((x^5 (1+x^8) (1+(-1+x) x (1+x^2)))/(-1+x (2+x (-1+(-1+x)^2 x^17)))) _Peter J. C. Moses_, Jun 01 2014
%t Table[Floor[(n(n-1))/19],{n,0,70}] (* or *) LinearRecurrence[ {2,-1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,-2,1},{0,0,0,0,0,1,1,2,2,3,4,5,6,8,9,11,12,14,16,18,20},70] (* _Harvey P. Dale_, May 25 2013 *)
%K nonn,easy
%O 0,8
%A _N. J. A. Sloane_.
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