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Search: id:A064510
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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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+0
4
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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
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Obviously all perfect numbers are included in this sequence.
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EXAMPLE
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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
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subtract = If[ #1 < #2, Throw[ #1], #1 - #2]&; f[n_] := Catch @ Fold[subtract, n, Divisors @ n] (from Bobby R. Treat, (DrBob(AT)bigfoot.com), Jul 14 2005)
l = {}; Do[ If[ f[n] == 0, AppendTo[l, n]], {n, 10^8}]; l (from Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 14 2005)
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CROSSREFS
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Cf. A109883, A109884, A109886.
Sequence in context: A072710 A069235 A118372 this_sequence A114274 A110926 A131906
Adjacent sequences: A064507 A064508 A064509 this_sequence A064511 A064512 A064513
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KEYWORD
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nonn,nice
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AUTHOR
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Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 06 2001
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EXTENSIONS
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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
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