A335417 a(n) = denominator of Sum_{k=2..A335138(n)} abs(A309229(n, k))/k.

6, 15, 20, 15, 4, 35, 360, 630, 420, 1386, 280, 5005, 280, 1287, 3080, 3465, 2520, 770, 27720, 9009, 5720, 16380, 360360, 10010, 360360, 3465, 40040, 25740, 360360, 323323, 1750320, 765765, 123760, 3423420, 720720, 4849845, 360360, 45045

Offset

1,1

Links

Table of n, a(n) for n=1..38.

Mathematica

nn = 41; f[n_] := n; h[n_] := DivisorSum[n, MoebiusMu[#] # &]; A = Accumulate[Table[Table[h[GCD[n, k]], {k, 1, nn}], {n, 1, nn}]]; B = -Abs[A]; B[[All, 1]] = Table[f[n], {n, 1, nn}]; b = 1 + Total[Sign[1 + Sign[Accumulate[Transpose[B]]]]]; d = Table[Sum[Abs[A[[n, k]]]/k, {k, 2, b[[n]]}], {n, 1, nn}]; Denominator[d]

Crossrefs

Cf. A309229, A335138. See A335416 for numerators.

Sequence in context: A002599 A001484 A217480 * A173680 A230209 A277951

Adjacent sequences: A335414 A335415 A335416 * A335418 A335419 A335420

Keyword

nonn,frac

Author

Mats Granvik, Jun 09 2020

Status

approved