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 A053618 a(n) = ceiling(C(n,4)/n). 6

%I

%S 0,0,0,1,1,3,5,9,14,21,30,42,55,72,91,114,140,170,204,243,285,333,385,

%T 443,506,575,650,732,819,914,1015,1124,1240,1364,1496,1637,1785,1943,

%U 2109,2285,2470,2665,2870,3086,3311,3548,3795,4054,4324

%N a(n) = ceiling(C(n,4)/n).

%H Colin Barker, <a href="/A053618/b053618.txt">Table of n, a(n) for n = 1..1000</a>

%H R. L. Graham and N. J. A. Sloane, <a href="http://dx.doi.org/10.1109/TIT.1980.1056141">Lower bounds for constant weight codes</a>, IEEE Trans. Inform. Theory, 26 (1980), 37-43.

%H <a href="/index/Rec#order_11">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,0,0,0,0,1,-3,3,-1).

%F a(n) = ( 2*n^3 - 12*n^2 + 22*n - 3 + 9*(-1)^n + 3*(1+(-1)^n)*(-1)^(n*(n-1)/2) - 6*(1 + (-1)^n)*(-1)^floor(n/4) )/48. - _Luce ETIENNE_, Jan 20 2015

%F G.f.: x^4*(x^2 - x + 1)*(x^4 + x^2 - x + 1) / ((x-1)^4*(x+1)*(x^2+1)*(x^4+1)). - _Colin Barker_, Jan 20 2015

%o (PARI) concat([0,0,0], Vec(x^4*(x^2-x+1)*(x^4+x^2-x+1) / ((x-1)^4*(x+1)*(x^2+1)*(x^4+1)) + O(x^100))) \\ _Colin Barker_, Jan 20 2015

%Y Cf. A007997, A008646, A032192, A053643, A053731, A053733.

%K nonn,easy

%O 1,6

%A _N. J. A. Sloane_, Mar 25 2000

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Last modified April 18 08:37 EDT 2019. Contains 322209 sequences. (Running on oeis4.)