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

Author

Walter Nissen

Keywords

• nonn
• easy
• nice

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)

Crossrefs

Cf. A002192, A000203, A051444, A004394.

See A034885 and A002093 for another version.

Programs

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 *)

Formula

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