A059460 Iteration of unitary-sigma function: a(1) = 2, a(n) = usigma(a(n-1)).

2, 3, 4, 5, 6, 12, 20, 30, 72, 90, 180, 300, 520, 756, 1120, 1584, 2040, 3888, 4148, 5580, 9600, 13416, 22176, 31680, 46800, 61880, 108864, 126880, 171864, 276480, 344232, 492480, 639600, 1039584, 1663200, 2306304, 3454080, 6390144

Offset: 1

Author

Yasutoshi Kohmoto

Keywords

• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..6000

Crossrefs

Cf. A007497, A034448.

Programs

Mathematica

f[n_] := Times @@ (1 + Power@@@ FactorInteger[n]); NestList[f, 2, 30] (* Amiram Eldar, Aug 11 2019 *)

Extensions

Corrected by Jud McCranie, Oct 28 2001