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 A132999 Imperfect numbers: Not equal to sum of proper divisors. 10
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Imperfect numbers are either deficient numbers or abundant numbers. REFERENCES C. A. Pickover, El prodigio de los numeros, RBA Coleccionables, 2007, p. 190. LINKS Ivan Panchenko, Table of n, a(n) for n = 1..10000 FORMULA a(n) ~ n. - Charles R Greathouse IV, Feb 06 2015 MAPLE with(numtheory): A132999:=n->`if`(sigma(n)=2*n, NULL, n): seq(A132999(n), n=1..100); # Wesley Ivan Hurt, Sep 11 2015 PROG (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 CROSSREFS Cf. A000396 (perfect numbers), A005100 (deficient numbers), A005101 (abundant numbers). Sequence in context: A004725 A129487 A097010 * A054027 A272978 A080907 Adjacent sequences:  A132996 A132997 A132998 * A133000 A133001 A133002 KEYWORD easy,nonn AUTHOR Omar E. Pol, Oct 13 2007 STATUS approved

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Last modified April 14 19:32 EDT 2021. Contains 342951 sequences. (Running on oeis4.)