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A252997 Numbers n such that sigma(x) - x = n has at least two solutions, with each x having the same squarefree kernel, where sigma(x) is the sum of divisor function (A000203). 2
218, 189648, 720240, 119967120, 129705984, 517941905, 707902440, 1321744320, 98890370304, 99080219520, 119922568640, 139834382688, 347612467648, 580542318720, 952717920000, 1064902900320, 1153644808680, 2255573174400, 3903820736256, 6859688278905, 10944640212480, 14424196864000 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Numbers n such that n = A001065(j) = A001065(k) and A007947(j) = A007947(k), where j != k.
LINKS
Carlos Rivera, Prime Puzzle 774. S(i) and Rad(i), The Prime Puzzles and Problems Connection.
EXAMPLE
218 is the sum of proper divisors of 250 and 160, and rad(250) = rad(160) = 10, hence 218 is in the sequence with j=250 and k=160.
Other examples of n and j, k:
For n = 189648, j = 95832, k = 85536.
For n = 720240, j = 288120, k = 246960.
For n = 119967120, j = 38755080, k = 34398000.
For n = 129705984, j = 71614464, k = 60424704.
CROSSREFS
Cf. A001065 (sum of proper divisors of n), A007947 (squarefree kernel of n).
Sequence in context: A209824 A230333 A060530 * A126829 A171406 A025406
KEYWORD
nonn
AUTHOR
Naohiro Nomoto, Dec 25 2014
EXTENSIONS
a(6) onward from Fred Schneider, Feb 07 2015
STATUS
approved

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Last modified July 22 10:48 EDT 2024. Contains 374490 sequences. (Running on oeis4.)