A160047 - OEIS

%I #13 Dec 07 2017 22:14:08

%S 1,1,1,1,2,1,6,3,4,6,60,5,20,10,28,35,280,140,2520,126,120,1260,27720,

%T 1155,5544,13860,40040,12870,360360,12012,360360,45045,21840,360360,

%U 350064,340340,4084080,2042040,1989680,1939938,15519504,369512,5173168

%N Denominator of the Harary number for the cycle graph C_n.

%C Extended to a(1)-a(2) using the formula.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HararyIndex.html">Harary Index</a>

%e 0, 1, 3, 5, 15/2, 10, 77/6, 47/3, 75/4, 131/6, ...

%t Denominator[Table[1 - Mod[n, 2] + n HarmonicNumber[Floor[(n - 1)/2]], {n, 43}]] (* _Eric W. Weisstein_, Dec 06 2017 *)

%Y Cf. A160046.

%K nonn

%O 1,5

%A _Eric W. Weisstein_, Apr 30 2009