A336671 Unitary barely 3-abundant: numbers m such that 3 < usigma(m)/m < usigma(k)/k for all numbers k < m, where usigma is the sum of unitary divisors function (A034448).

30030, 39270, 43890, 46410, 51870, 62790, 67830, 79170, 82110, 91770, 103530, 161070, 166530, 709170, 718410, 723030, 732270, 764610, 778470, 801570, 806190, 815430, 829290, 833910, 847770, 861630, 875490, 884730, 155934030, 264670770, 1234205070, 1448478570

Offset

1,1

Comments

The corresponding values of usigma(m)/m are 3.222..., 3.168...., 3.149..., 3.127..., 3.109..., ...

Links

Amiram Eldar, Table of n, a(n) for n = 1..36

Mathematica

usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); s = {}; rm = 4; Do[r = usigma[n]/n; If[r > 3 && r < rm, rm = r; AppendTo[s, n]], {n, 1, 10^5}]; s

Crossrefs

The unitary version of A259312.

Subsequence of A285615.

Cf. A034448, A034683, A302570, A336672.

Sequence in context: A066765 A067885 A285615 * A258361 A072940 A147573

Adjacent sequences: A336668 A336669 A336670 * A336672 A336673 A336674

Keyword

nonn

Author

Amiram Eldar, Jul 29 2020

Status

approved