

A069146


Numbers m such that m = sigma(abs(k))  3k, where k = sigma(m)  3m.


1



1248, 1596, 28272, 30240, 32760, 463296, 2178540, 12865770, 23569920, 30998250, 45532800, 142990848, 1379454720, 1912369152, 2623977450, 43861478400, 66433720320, 153003540480, 403031236608, 489622536192, 704575228896
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OFFSET

1,1


COMMENTS

1.5*10^12 < a(22) <= 7834005405696. If 2^k1 > 3 is a prime (A000023), then 2^(k1)*3*19*(2^k1) is a term.  Giovanni Resta, Dec 11 2019


LINKS

Table of n, a(n) for n=1..21.


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

Cf. A000203, A069085, A001065.
Sequence in context: A066696 A195006 A114528 * A251648 A235021 A184500
Adjacent sequences: A069143 A069144 A069145 * A069147 A069148 A069149


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



