A181596 Abundance of A181595(n).

4, 3, 2, 12, 10, 8, 4, 2, 7, 56, 78, 8, 2, 2, 32, 16, 4, 2, 532, 152, 136, 8, 68, 31, 992, 128, 8, 64, 32, 16, 4, 8, 128, 32, 8, 2, 43648, 2528, 32, 4, 2, 32, 2272, 32, 32, 127, 16256, 32, 32, 4, 536, 8, 32, 8, 52, 16, 32, 41044, 64, 512, 128, 64, 16, 4, 2, 8

Offset

1,1

Comments

a(n) is a proper divisor of A181595(n).

Links

Michel Marcus, Table of n, a(n) for n = 1..200

Paul Pollack and Vladimir Shevelev, On perfect and near-perfect numbers, J. Number Theory 132 (2012), pp. 3037-3046. arXiv:1011.6160

Formula

a(n) = A033880(A181595(n)).

Example

Since A181595(1)=12, a(1)=sigma(12)-2*12=28-24=4.

Mathematica

Reap[For[n = 12, n <= 2 10^7, n++, abn = DivisorSigma[1, n] - 2n; If[1 < abn < n && Divisible[n, abn], Print[{n, abn}]; Sow[abn]]]][[2, 1]] (* Jean-François Alcover, Oct 28 2018 *)

Crossrefs

Cf. A181595, A000396, A005101, A153501, A005820.

Sequence in context: A333780 A033882 A062111 * A182142 A033881 A099406

Adjacent sequences: A181593 A181594 A181595 * A181597 A181598 A181599

Keyword

nonn

Author

Vladimir Shevelev, Nov 01 2010

Extensions

a(10)-a(11) corrected by Vladimir Shevelev, Nov 03 2010

Entries checked, definition shortened by R. J. Mathar, Nov 17 2010

More terms from Michel Marcus, Feb 06 2016

Status

approved