A007626 Sum of divisors of superabundant numbers (A004394).

1, 3, 7, 12, 28, 60, 91, 124, 168, 360, 546, 744, 1170, 2418, 2880, 4368, 5952, 9360, 19344, 39312, 59520, 99944, 112320, 232128, 471744, 714240, 1199328, 1451520, 2437344, 2926080, 3249792, 6604416, 9999360

Offset

1,2

Comments

Local maxima of sigma(n), the sum of divisors function A000203.

Same as A063072 for the first 19 terms. - T. D. Noe, Jul 01 2008

Links

Amiram Eldar, Table of n, a(n) for n = 1..6863 (terms 1..500 from T. D. Noe)

Formula

a(n) = A000203(A004394(n)). - Amiram Eldar, Sep 25 2021

Mathematica

Reap[ For[ n=1; a=0, n <= 3*10^6, n++, s = DivisorSigma[1, n]; b = s/n; If[ b>a, a=b; Print[s]; Sow[s]]]][[2, 1]] (* Jean-François Alcover, Apr 02 2013 *)
Join[{1}, DeleteDuplicates[Select[{#[[1]], #[[2]], #[[2]]/#[[1]]}&/@Table[ {n, DivisorSigma[1, n]}, {n, 10^6}], #[[3]]>1&], GreaterEqual[#1[[3]], #2[[3]]]&][[All, 2]]] (* The program generates the first 31 terms of the sequence. *) (* Harvey P. Dale, Oct 04 2022 *)

Crossrefs

Cf. A002192, A000203, A051444, A004394.

See A034885 and A002093 for another version.

Sequence in context: A256259 A182941 A063072 * A193297 A240738 A047068

Adjacent sequences: A007623 A007624 A007625 * A007627 A007628 A007629

Keyword

nonn,easy,nice

Author

Walter Nissen

Status

approved