|
|
A055489
|
|
Largest number x such that sum of divisors of x is n!.
|
|
5
|
|
|
5, 23, 95, 719, 5039, 39917, 361657, 3624941, 39904153, 479001599, 6226862869, 87178291199, 1307672080867, 20922780738961, 355687390376431, 6402373545694717, 121645099711277873, 2432902005056589697, 51090942157413850441
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
3,1
|
|
COMMENTS
|
For n = 1, a(1) = 1; for n = 2 there is no solution.
|
|
REFERENCES
|
R. K. Guy (1981): Unsolved Problems In Number Theory, B39.
|
|
LINKS
|
|
|
FORMULA
|
|
|
EXAMPLE
|
For n = 6, the 15 solutions are as follows: {264, 270, 280, 354, 376, 406, 418, 435, 459, 478, 537, 623, 649, 667, 719}.
|
|
PROG
|
(PARI) a(n) = {fn = n!; x = fn - 1; while(sigma(x) != fn, x--); x; } \\ Michel Marcus, Dec 17 2013
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|