A334721 Denominator of the product of n and the n-th harmonic alternating number, Sum_{k=1..n} (-1)^(k+1)/k.

1, 1, 2, 3, 12, 10, 60, 105, 280, 252, 2520, 2310, 27720, 25740, 24024, 9009, 144144, 136136, 2450448, 11639628, 11085360, 10581480, 232792560, 223092870, 1070845776, 1029659400, 2974571600, 2868336900, 11473347600, 11090902680, 332727080400, 644658718275, 625123605600

Offset: 1

Author

Petros Hadjicostas, May 08 2020

Keywords

• nonn
• frac

Comments

For n = 1 to 15, we have a(n) = A002944, but a(16) = 9009 <> 45045 = A002944(16).

Examples

			The first few fractions are 1, 1, 5/2, 7/3, 47/12, 37/10, 319/60, 533/105, 1879/280, ... = A119787/A334721.
		

Crossrefs

Cf. A002944, A119787 (numerators).

Programs

PARI

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