A178601 a(n) = s(s(n)), where s(n) = sigma(n)-n = A001065(n).

0, 0, 1, 0, 6, 0, 1, 3, 7, 0, 15, 0, 8, 4, 9, 0, 11, 0, 14, 1, 10, 0, 55, 6, 15, 1, 28, 0, 54, 0, 1, 9, 22, 1, 17, 0, 14, 1, 43, 0, 66, 0, 50, 15, 16, 0, 64, 7, 1, 11, 26, 0, 78, 1, 63, 1, 31, 0, 172, 0, 20, 1, 41, 1, 90, 0, 32, 13, 40, 0, 45, 0, 50, 8, 63, 1, 144, 0, 56, 50, 40, 0, 196, 1, 26, 15, 76, 0, 259, 11, 64, 13, 43, 6, 236, 0

Offset: 2

Author

Roger L. Bagula, May 30 2010

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 2..16384
• Carl Pomerance, The first function and its iterates, pp. 125-138 in Connections in Discrete Mathematics, ed. S. Butler et al., Cambridge, 2018.
• Index entries for sequences related to sums of divisors

Crossrefs

Cf. A001065, A000203, A051027, A072869.

Cf. A206708 (fixed points, union of A000396 and A063990). - Antti Karttunen, Nov 01 2017

Programs

Mathematica

Table[Apply[ Plus, Divisors[Apply[ Plus, Divisors[n]] - n]] - (Apply[Plus, Divisors[n]] - n), {n, 0, 100}]

PARI

A001065(n) = (sigma(n) - n);
A178601(n) = A001065(A001065(n)); \\ Antti Karttunen, Nov 01 2017

Extensions

Edited by N. J. A. Sloane, May 30 2010

Terms a(0) and a(1) removed and more terms added by Antti Karttunen, Nov 01 2017