This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 15 03:48 EST 2019. Contains 329990 sequences. (Running on oeis4.)