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A066469
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Numbers having just four anti-divisors.
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0
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13, 18, 40, 41, 61, 84, 100, 169, 289, 421, 784, 1024, 1104, 1296, 3121, 5776, 9216, 12544, 12769, 13924, 16129, 17956, 24649, 32761, 33024, 35344, 36721, 36864, 38809, 71821, 75076
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| See A066272 for definition of anti-divisor.
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LINKS
| Jon Perry, The Anti-Divisor
Jon Perry, The Anti-divisor [Cached copy]
Jon Perry, The Anti-divisor: Even More Anti-Divisors [Cached copy]
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MATHEMATICA
| antid[n_] := Select[ Union[ Join[ Select[ Divisors[2n - 1], OddQ[ # ] && # != 1 & ], Select[ Divisors[2n + 1], OddQ[ # ] && # != 1 & ], 2n/Select[ Divisors[ 2*n], OddQ[ # ] && # != 1 &]]] }, # < n & ]]; Select[ Range[10^5], Length[ antid[ # ]] == 4 & ]
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CROSSREFS
| Cf. A066272.
Sequence in context: A176555 A131019 A037158 * A197704 A119149 A171098
Adjacent sequences: A066466 A066467 A066468 * A066470 A066471 A066472
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 02 2002
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