%I #8 May 09 2020 07:22:46

%S 1,2,3,6,20,20,105,210,504,504,4620,4620,51480,51480,9009,18018,

%T 272272,272272,23279256,23279256,21162960,21162960,446185740,

%U 446185740,2059318800,2059318800,5736673800,5736673800,22181805360,22181805360,644658718275,1289317436550,1213475234400

%N Denominator of the sum of all elements of the n X n matrix M with M[i,j] = (-1)^(i+j)*i/j for i,j = 1..n.

%e The absolute values of the first few fractions are 1, 1/2, 5/3, 7/6, 47/20, 37/20, 319/105, 533/210, 1879/504, ... = A120301/A334724.

%o (PARI) a(n) = denominator(sum(j=1, n, sum(i=1, n, (-1)^(i+j)*i/j))); \\ _Michel Marcus_, May 09 2020

%Y Cf. A120301 (absolute values of numerators).

%K nonn,frac

%O 1,2

%A _Petros Hadjicostas_, May 09 2020

%E More terms from _Michel Marcus_, May 09 2020