A204830 Numbers n whose divisors can be partitioned into three disjoint sets whose sums are all sigma(n)/3.

120, 180, 240, 360, 420, 480, 504, 540, 600, 660, 672, 720, 780, 840, 960, 1080, 1260, 1320, 1440, 1512, 1560, 1584, 1620, 1680, 1800, 1848, 1890, 1920, 1980, 2016, 2040, 2160, 2184, 2280, 2340, 2352, 2376, 2400, 2520, 2640, 2688, 2760, 2772, 2856, 2880, 2940, 3000

Offset

1,1

Comments

Subsequence of A023197.

Links

Paolo P. Lava, Table of n, a(n) for n = 1..500

Farid Jokar, On k-layered numbers, arXiv:2207.09053 [math.NT], 2022.

Example

Number 180 is in sequence because sigma(180)/3 = 182 = 2+180 = 1+3+4+5+6+9+10+15+18+30+36+45 = 12+20+60+90 (summands are all divisors of 180).

Crossrefs

Cf. A083207 (Zumkeller numbers-numbers n whose divisors can be partitioned into two disjoint sets whose sums are both sigma(n)/2), A204831 (numbers n whose divisors can be partitioned into four disjoint sets whose sums are all sigma(n)/4).

Sequence in context: A337386 A023197 A204828 * A279088 A337479 A322377

Adjacent sequences: A204827 A204828 A204829 * A204831 A204832 A204833

Keyword

nonn

Author

Jaroslav Krizek, Jan 22 2012

Status

approved