OFFSET
2,1
FORMULA
n>=2: a(n) = denominator(max_{k=2..n}(A191898(n, k)/k)).
EXAMPLE
max(-1/2) = -1/2 therefore a(2) = 2,
max(1/2, -2/3) = 1/2 therefore a(3) = 2,
max(-1/2, 1/3, -1/4) = 1/3 therefore a(4) = 3,
max(1/2, 1/3, 1/4, -4/5) = 1/2 therefore a(5) = 2
max(-1/2, -2/3, -1/4, 1/5, 1/3) = 1/3 therefore a(6) = 3,
max(1/2, 1/3, 1/4, 1/5, 1/6, -6/7) = 1/2 therefore a(7) = 2,
max(-1/2, 1/3, -1/4, 1/5, -1/6, 1/7, -1/8) = 1/3 therefore a(8) = 3,
max(1/2, -2/3, 1/4, 1/5, -1/3, 1/7, 1/8, -2/9) = 1/2 therefore a(9) = 2,
max(-1/2, 1/3, -1/4, -4/5, -1/6, 1/7, -1/8, 1/9, 2/5) = 2/5 therefore a(10) = 5.
MATHEMATICA
a[n_] := DivisorSum[n, MoebiusMu[#] # &]; nn = 78; Denominator[Table[Max[Table[a[GCD[n, k]]/k, {k, 2, n}]], {n, 2, nn}]]
CROSSREFS
KEYWORD
nonn,frac
AUTHOR
Mats Granvik, Apr 19 2021
STATUS
approved