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

Author

Vladimir Shevelev, Nov 01 2010

Keywords

• nonn

Comments

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

Examples

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

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

Crossrefs

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

Programs

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 *)

Formula

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

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