OFFSET
1,1
COMMENTS
1.5*10^12 < a(22) <= 7834005405696. If 2^k-1 > 3 is a prime (A000023), then 2^(k-1)*3*19*(2^k-1) is a term. - Giovanni Resta, Dec 11 2019
EXAMPLE
Let n = 1248. The sum of the divisors of n is 3528, so k = 3528 - 3*1248 = -216. The sum of the divisors of 216 is 600 and 600 - 3*(-216) = 1248, so 1248 is in the sequence.
MATHEMATICA
Select[Range[5*10^5], DivisorSigma[1, Abs[(k = DivisorSigma[1, #] - 3#)]] -3k == # &] (* Amiram Eldar, Dec 11 2019 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jason Earls, Apr 08 2002
EXTENSIONS
More terms from David Wasserman, Apr 15 2003
a(12)-a(15) from Amiram Eldar, Dec 11 2019
a(16)-a(21) from Giovanni Resta, Dec 11 2019
STATUS
approved