OFFSET
1,1
COMMENTS
If m is a term then so is m*p^k when p is coprime to m. - David A. Corneth, Mar 09 2024
Is this sequence equal to the sequence: "Numbers k such that sigma(k) is divisible by 3 and sigma(k) >= 3*k"? - David A. Corneth, Mar 17 2024
Answer: No. The numbers k with sigma(k) >= 3k and sigma(k) divisible by 3 that are not in this sequence are in A306476. - Amiram Eldar, Jun 22 2024
LINKS
David A. Corneth, Table of n, a(n) for n = 1..10296 (first 500 terms from Paolo P. Lava, terms <= 550000).
Farid Jokar, On k-layered numbers, arXiv:2207.09053 [math.NT], 2022.
EXAMPLE
180 is a term 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 the divisors of 180).
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jan 22 2012
STATUS
approved