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 A183857 a(n) = n - 1 + ceiling((2/3)*n^2); complement of A183874. 1

%I

%S 1,4,8,14,21,29,39,50,62,76,91,107,125,144,164,186,209,233,259,286,

%T 314,344,375,407,441,476,512,550,589,629,671,714,758,804,851,899,949,

%U 1000,1052,1106,1161,1217,1275,1334,1394,1456,1519,1583,1649,1716,1784,1854,1925,1997,2071

%N a(n) = n - 1 + ceiling((2/3)*n^2); complement of A183874.

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,1,-2,1).

%F a(n) = n - 1 + ceiling((2/3)n^2).

%t a=3/2; b=0;

%t Table[n+Floor[(a*n+b)^(1/2)],{n,100}]

%t Table[n-1+Ceiling[(n*n-b)/a],{n,80}]

%t LinearRecurrence[{2,-1,1,-2,1},{1,4,8,14,21},60] (* _Harvey P. Dale_, Apr 12 2020 *)

%Y Cf. A183874.

%K nonn,easy

%O 1,2

%A _Clark Kimberling_, Jan 07 2011

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Last modified September 24 12:38 EDT 2021. Contains 347642 sequences. (Running on oeis4.)