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A064510
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Numbers n such that the sum of the first k divisors of n is equal to n for some k.
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8
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1, 6, 24, 28, 496, 2016, 8128, 8190, 42336, 45864, 392448, 714240, 1571328, 33550336, 61900800, 91963648, 211891200, 1931236608, 2013143040, 4428914688, 8589869056, 10200236032, 137438691328, 214204956672
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Obviously all perfect numbers are included in this sequence.
Other than perfect numbers, 104828758917120, 916858574438400, 967609154764800, 93076753068441600 and 215131015678525440 are also in the sequence (not necessarily the next five terms). - Donovan Johnson, Sep 05 2011
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EXAMPLE
| Divisors of 24 are 1, 2, 3, 4, 6, 8, 12 and 24 and 1+2+3+4+6+8=24
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MATHEMATICA
| subtract = If[ #1 < #2, Throw[ #1], #1 - #2]&; f[n_] := Catch @ Fold[subtract, n, Divisors @ n]; lst = {}; Do[ If[ f[n] == 0, AppendTo[lst, n]], {n, 10^8}]; lst (* from Bobby R. Treat and Robert G. Wilson v, Jul 14 2005 *)
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CROSSREFS
| Cf. A109883, A109884, A109886, A185584, A194472.
Sequence in context: A069235 A175200 A118372 * A114274 A110926 A131906
Adjacent sequences: A064507 A064508 A064509 * A064511 A064512 A064513
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KEYWORD
| nonn,nice
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AUTHOR
| Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 06 2001
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EXTENSIONS
| More terms from Don Reble (djr(AT)nk.ca), Dec 17 2001
a(19)-a(23) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Aug 31 2008
a(24) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Aug 11 2011
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