|
Search: id:A037020
|
|
|
| A037020 |
|
Numbers n such that sum of proper (or aliquot) divisors of n is a prime. |
|
+0
8
|
|
| 4, 8, 21, 27, 32, 35, 39, 50, 55, 57, 63, 65, 77, 85, 98, 111, 115, 125, 128, 129, 155, 161, 171, 175, 185, 187, 189, 201, 203, 205, 209, 221, 235, 237, 242, 245, 265, 275, 279, 291, 299, 305, 309, 319, 323, 324, 325, 327, 335, 338, 341, 365, 371, 377, 381
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Assuming the Goldbach conjecture, it is easy to show that all primes, except 2 and 5, are the sum of the proper divisors of some number. (T. D. Noe, Nov 29 2006).
|
|
LINKS
|
T. D. Noe, Table of n, a(n) for n=1..10000
|
|
EXAMPLE
|
a(4)=27 because the aliquot divisors of 27 are 1 3 9, whose sum is 13, prime.
|
|
MATHEMATICA
|
Select[Range[300], PrimeQ[Plus @@ Take[Divisors[ # ], {1, Length[Divisors[ # ]] - 1 }]] &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Apr 08 2006
|
|
CROSSREFS
|
Cf. A001065
Sequence in context: A086912 A000585 A102559 this_sequence A094878 A079860 A006908
Adjacent sequences: A037017 A037018 A037019 this_sequence A037021 A037022 A037023
|
|
KEYWORD
|
nonn,easy,nice
|
|
AUTHOR
|
Felice Russo (felice.russo(AT)katamail.com)
|
|
|
Search completed in 0.002 seconds
|
