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A072869 a(n) = sigma(sigma(n)-n), where sigma = A000203, sum of the divisors of n. 5
1, 1, 4, 1, 12, 1, 8, 7, 15, 1, 31, 1, 18, 13, 24, 1, 32, 1, 36, 12, 24, 1, 91, 12, 31, 14, 56, 1, 96, 1, 32, 24, 42, 14, 72, 1, 36, 18, 93, 1, 120, 1, 90, 48, 42, 1, 140, 15, 44, 32, 72, 1, 144, 18, 127, 24, 63, 1, 280, 1, 54, 42, 104, 20, 168, 1, 90, 40, 114, 1, 168, 1, 90, 57 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,3

LINKS

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

Index entries for sequences related to sums of divisors

FORMULA

a(n) = A000203(A001065(n)). - Michel Marcus, Nov 26 2013

For p prime, a(p) = 1. - Michel Marcus, Nov 19 2014

MATHEMATICA

Table[DivisorSigma[1, DivisorSigma[1, n]-n], {n, 2, 80}] (* Harvey P. Dale, Sep 23 2013 *)

PROG

(PARI) A072869(n) = sigma(sigma(n)-n); \\ Antti Karttunen, Oct 30 2017

CROSSREFS

Cf. A000203 (sigma(n)), A001065 (sigma(n) - n), A051027.

Sequence in context: A097877 A225770 A019304 * A064279 A078710 A175763

Adjacent sequences:  A072866 A072867 A072868 * A072870 A072871 A072872

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Jul 27 2002

STATUS

approved

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Last modified February 25 21:00 EST 2020. Contains 332258 sequences. (Running on oeis4.)