A059775 - OEIS

%I #9 Feb 06 2015 16:08:56

%S 0,24,120,360,824,1664,2992,5000,7848,11808,17024,23888,32576,43432,

%T 56816,73136,92616,115872,143104,174928,211808,254312,302680,357832,

%U 420136,490232,568664,656360,753496,861376,980232,1111016,1254504

%N From solution to a counting problem.

%H Emeric Deutsch, Murray S. Klamkin and Denis Constales, <a href="http://www.jstor.org/stable/2695540">Solution to Problem 10540: Counting the Solutions</a>, Amer. Math. Monthly, 108 (Feb. 2001), 172-173.

%p [seq(n*(n-1)*(n^2-n-1) + 4*add(floor(n/k^2)*phi(k),k=2..floor(sqrt(n))) - 2*add(floor(n/k)^2*phi(k),k=2..n), n=2..30)];

%K nonn

%O 0,2

%A _N. J. A. Sloane_, Feb 21 2001