A334724 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.

1, 2, 3, 6, 20, 20, 105, 210, 504, 504, 4620, 4620, 51480, 51480, 9009, 18018, 272272, 272272, 23279256, 23279256, 21162960, 21162960, 446185740, 446185740, 2059318800, 2059318800, 5736673800, 5736673800, 22181805360, 22181805360, 644658718275, 1289317436550, 1213475234400

Offset: 1

Author

Petros Hadjicostas, May 09 2020

Keywords

• nonn
• frac

Examples

			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.
		

Crossrefs

Cf. A120301 (absolute values of numerators).

Programs

PARI

a(n) = denominator(sum(j=1, n, sum(i=1, n, (-1)^(i+j)*i/j))); \\ Michel Marcus, May 09 2020

Extensions

More terms from Michel Marcus, May 09 2020