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A008363 a(n) = floor(n/5)*ceiling(n/5). 0

%I

%S 0,0,0,0,0,1,2,2,2,2,4,6,6,6,6,9,12,12,12,12,16,20,20,20,20,25,30,30,

%T 30,30,36,42,42,42,42,49,56,56,56,56,64,72,72,72,72,81,90,90,90,90,

%U 100,110,110,110,110,121,132,132

%N a(n) = floor(n/5)*ceiling(n/5).

%F From _R. J. Mathar_, Mar 11 2012: (Start)

%F a(n) = a(n-1) +2 a(n-5) -2 a(n-6) -a(n-10) +a(n-11).

%F G.f.: x^5*(1+x)/((1-x)^3*(1+x+x^2+x^3+x^4)^2). (End)

%K nonn

%O 0,7

%A _N. J. A. Sloane_

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Last modified August 5 05:22 EDT 2020. Contains 336209 sequences. (Running on oeis4.)