A348865 Numbers k such that A099378(k) | (A099377(k) - 1).

1, 2, 3, 6, 9, 14, 15, 24, 28, 30, 32, 42, 44, 55, 84, 91, 95, 120, 135, 140, 182, 198, 224, 234, 243, 261, 270, 308, 330, 351, 420, 444, 459, 477, 483, 492, 496, 546, 564, 570, 625, 630, 636, 672, 744, 756, 840, 852, 861, 924

Offset

1,2

Comments

A disjoint union of the harmonic numbers (A001599) and the numbers whose harmonic mean of divisors is of the form m + 1/k, where m and k are integers.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

2 is a term since the harmonic mean of divisors of 2 is 4/3 and 3 | (4-1).

Mathematica

h[n_] := DivisorSigma[0, n]/DivisorSigma[-1, n]; q[n_] := Divisible[Numerator[(h1 = h[n])] - 1, Denominator[h1]]; Select[Range[1000], q]

Crossrefs

Cf. A001599, A099377, A099378, A348866.

Sequence in context: A128955 A215523 A306247 * A244739 A075123 A023559

Adjacent sequences: A348862 A348863 A348864 * A348866 A348867 A348868

Keyword

nonn

Author

Amiram Eldar, Nov 02 2021

Status

approved