OFFSET
1,1
COMMENTS
Also the ratio of the numerators of n*H'(n) = A119787(n) and H'(n) = A058313(n) when they are different. (H'(n) is the alternating harmonic number H'(n) = Sum_{k=1..n} (-1)^(k+1)*1/k.)
It appears that most a(n) are prime divisors of the corresponding indices A121594(n).
It appears that all a(n) belong to A092579(n), which is a sieve using the Fibonacci sequence over the integers >= 2. [Edited by Petros Hadjicostas, May 11 2020]
MATHEMATICA
Do[H=Sum[(-1)^(i+1)*1/i, {i, 1, n}]; a=Numerator[n*H]; b=Numerator[H]; If[ !Equal[a, b], Print[{n, a/b}]], {n, 1, 6000}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Alexander Adamchuk, Aug 09 2006
STATUS
approved