The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 (list; graph; refs; listen; history; text; internal format)
 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 LINKS 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 4 15:36 EST 2021. Contains 349526 sequences. (Running on oeis4.)