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a(n) = floor(n^2/9).
11

%I #35 Aug 21 2024 12:26:53

%S 0,0,0,1,1,2,4,5,7,9,11,13,16,18,21,25,28,32,36,40,44,49,53,58,64,69,

%T 75,81,87,93,100,106,113,121,128,136,144,152,160,169,177,186,196,205,

%U 215,225,235,245,256,266,277,289,300,312,324,336,348

%N a(n) = floor(n^2/9).

%H Paolo Xausa, <a href="/A056838/b056838.txt">Table of n, a(n) for n = 0..10000</a>

%H <a href="/index/Rec#order_11">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,0,0,0,0,0,0,1,-2,1).

%F G.f.: x^3*(1+x)*(x^2-x+1)^2/((1-x)^3*(1+x+x^2)(x^6+x^3+1)). [_R. J. Mathar_, Jan 05 2009]

%t Floor[Range[0, 100]^2/9] (* _Paolo Xausa_, Aug 21 2024 *)

%Y Cf. A008740.

%Y Cf. A000290, A007590, A000212, A002620, A118015, A056827, A056834, A130519, A056865.

%K nonn,easy

%O 0,6

%A _N. J. A. Sloane_, Sep 02 2000