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

1,2

Links

Table of n, a(n) for n=1..33.

Example

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.

Prog

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

Crossrefs

Cf. A120301 (absolute values of numerators).

Sequence in context: A093447 A321203 A259456 * A328218 A254441 A336461

Adjacent sequences: A334721 A334722 A334723 * A334725 A334726 A334727

Keyword

nonn,frac

Author

Petros Hadjicostas, May 09 2020

Extensions

More terms from Michel Marcus, May 09 2020

Status

approved