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A132999
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Imperfect numbers: Not equal to sum of proper divisors.
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10
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1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69
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OFFSET
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1,2
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COMMENTS
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Imperfect numbers are either deficient numbers or abundant numbers.
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REFERENCES
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C. A. Pickover, El prodigio de los numeros, RBA Coleccionables, 2007, p. 190.
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LINKS
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Ivan Panchenko, Table of n, a(n) for n = 1..10000
Omar E. Pol, Determinacion geometrica de los numeros primos y perfectos.
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FORMULA
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a(n) ~ n. - Charles R Greathouse IV, Feb 06 2015
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MAPLE
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with(numtheory): A132999:=n->`if`(sigma(n)=2*n, NULL, n): seq(A132999(n), n=1..100); # Wesley Ivan Hurt, Sep 11 2015
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PROG
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(PARI) is(n)=sigma(n, -1)!=2 \\ Charles R Greathouse IV, Feb 06 2015
(Magma) [n: n in [1..120] | not SumOfDivisors(n) eq 2*n]; // Vincenzo Librandi, Sep 12 2015
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CROSSREFS
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Cf. A000396 (perfect numbers), A005100 (deficient numbers), A005101 (abundant numbers).
Sequence in context: A129487 A097010 A351227 * A054027 A272978 A080907
Adjacent sequences: A132996 A132997 A132998 * A133000 A133001 A133002
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KEYWORD
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easy,nonn
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AUTHOR
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Omar E. Pol, Oct 13 2007
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STATUS
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approved
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