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A178601 a(n) = s(s(n)), where s(n) = sigma(n)-n = A001065(n). 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,5

REFERENCES

Carl Pomerance, The first function and its iterates, pp. 125-138 in Connections in Discrete Mathematics, ed. S. Butler et al., Cambridge, 2018.

LINKS

Antti Karttunen, Table of n, a(n) for n = 2..16384

Index entries for sequences related to sums of divisors

MATHEMATICA

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

PROG

(PARI)

A001065(n) = (sigma(n) - n);

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

CROSSREFS

Cf. A001065, A000203,  A051027, A072869.

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

Sequence in context: A020796 A011253 A049248 * A094691 A095715 A321215

Adjacent sequences:  A178598 A178599 A178600 * A178602 A178603 A178604

KEYWORD

nonn

AUTHOR

Roger L. Bagula, May 30 2010

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

STATUS

approved

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Last modified November 15 06:05 EST 2019. Contains 329144 sequences. (Running on oeis4.)