A097989 Numbers n such that n=tau_3(n)=A007425(n).

1, 3, 18, 36

Offset

1,2

Comments

Also, numbers n such that n = sum_d|n (tau(d)), (i.e. n is equal to the total number of divisors of all divisors of n ). - Lekraj Beedassy, Jul 12 2008

References

J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 36, pp 14, Ellipses, Paris 2008.

J.-M. De Koninck & A. Mercier, 1001 Problemes en Theorie Classique Des Nombres, Problem 712 pp. 93;305 Ellipses Paris 2004.

Links

Table of n, a(n) for n=1..4.

Mathematica

Select[Range[10^5], Total[(DivisorSigma[0, #]&) /@ Divisors[#]] == #&](* Jean-François Alcover, Sep 14 2011 *)

Crossrefs

Sequence in context: A108169 A063116 A125284 * A039700 A069147 A337921

Adjacent sequences: A097986 A097987 A097988 * A097990 A097991 A097992

Keyword

fini,full,nonn

Author

Lekraj Beedassy, Sep 07 2004

Status

approved