login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
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

Omar E. Pol, Determinacion geometrica de los numeros primos y perfectos.

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: A129487 A097010 A351227 * 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 29 02:42 EST 2023. Contains 359915 sequences. (Running on oeis4.)