|
|
A242871
|
|
Numbers n such that (n^n-3^3)/(n-3) is an integer.
|
|
3
|
|
|
1, 2, 4, 5, 6, 7, 9, 11, 12, 15, 19, 21, 23, 27, 30, 35, 39, 42, 43, 45, 51, 57, 63, 67, 75, 81, 83, 87, 99, 103, 111, 120, 123, 129, 131, 147, 159, 163, 171, 183, 195, 203, 219, 223, 237, 243, 255, 259, 275, 291, 297, 303, 315, 323, 331, 339, 345, 354, 363, 381, 387
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,2
|
|
COMMENTS
|
These are also numbers n such that (n^3-3^n)/(n-3) is an integer.
|
|
LINKS
|
|
|
EXAMPLE
|
(5^5-3^3)/(5-3) = 3098/2 = 1549 is an integer. Thus 5 is a member of this sequence.
|
|
MAPLE
|
filter:= proc(n) (n^n - 27) mod (n-3) = 0 end proc:
|
|
MATHEMATICA
|
Join[{1, 2}, Select[Range[4, 400], IntegerQ[(#^#-27)/(#-3)]&]] (* Harvey P. Dale, Dec 17 2014 *)
|
|
PROG
|
(PARI) for(n=1, 1000, if(n!=3, s=(n^n-3^3)/(n-3); if(floor(s)==s, print(n))))
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|