|
Search: id:A072234
|
|
|
| A072234 |
|
Numbers n such that reverse(n) = sum of the proper divisors of n. |
|
+0
2
|
| |
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
I call these the "tcefrep numbers" ("perfect" spelled backwards). This sequence lists all tcefrep numbers up to 2.28 * 10^8. Mark Ganson conjectures that all tcefrep numbers are divisible by 3.
Jens Kruse Andersen discovered that 4158499614 is tcefrep (though this may not be the next term). There are no more tcefrep numbers < 10^10.
|
|
EXAMPLE
|
The proper divisors of 498906 are 1, 2, 3, 6, 9, 18, 27, 54, 9239, 18478, 27717, 55434, 83151, 166302, 249453, which sum to 609894, the reverse of 498906; hence 498906 is tcefrep.
|
|
MATHEMATICA
|
f[n_] := FromDigits[Reverse[IntegerDigits[n]]]; Do[ If[f[n] == Apply[Plus, Drop[Divisors[n], -1]], Print[n]], {n, 2, 10^9}]
|
|
CROSSREFS
|
Cf. A069942.
Adjacent sequences: A072231 A072232 A072233 this_sequence A072235 A072236 A072237
Sequence in context: A112642 A067503 A079288 this_sequence A115476 A116272 A067484
|
|
KEYWORD
|
base,more,nonn,nice
|
|
AUTHOR
|
Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jul 05 2002
|
|
|
Search completed in 0.002 seconds
|
