A072869 a(n) = sigma(sigma(n)-n), where sigma = A000203, sum of the divisors of n.

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

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 * A369905 A064279 A369908

Adjacent sequences: A072866 A072867 A072868 * A072870 A072871 A072872

Keyword

easy,nonn

Author

Benoit Cloitre, Jul 27 2002

Status

approved