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a(n) = largest m such that m*(m+1)/2 <= 14*n.
5

%I #8 Dec 22 2012 13:12:22

%S 0,4,7,8,10,11,12,13,14,15,16,17,17,18,19,20,20,21,21,22,23,23,24,24,

%T 25,25,26,27,27,28,28,28,29,29,30,30,31,31,32,32,32,33,33,34,34,35,35,

%U 35,36,36,36,37,37,38,38,38,39,39,39,40,40,40,41,41,41,42,42,42,43,43,43,44,44,44,45,45,45,45,46,46,46,47,47,47,48,48,48,48,49,49,49,49,50

%N a(n) = largest m such that m*(m+1)/2 <= 14*n.

%C Created in an attempt to simplify the definition of certain sequences currently under review by the editors.

%H Harvey P. Dale, <a href="/A214206/b214206.txt">Table of n, a(n) for n = 0..1000</a>

%F a(n) = A003056(14*n). - _R. J. Mathar_, Jul 09 2012

%e 4*5/2 <= 14 but 5*6/2 > 14, so a(1)=4.

%t Array[Floor[(Sqrt[1+112#]-1)/2]&,100,0] (* _Harvey P. Dale_, Dec 22 2012 *)

%K nonn

%O 0,2

%A _N. J. A. Sloane_, Jul 08 2012