|
| |
|
|
A133195
|
|
Smallest number whose sum of digits is 3n.
|
|
1
|
|
|
|
0, 3, 6, 9, 39, 69, 99, 399, 699, 999, 3999, 6999, 9999, 39999, 69999, 99999, 399999, 699999, 999999, 3999999, 6999999, 9999999, 39999999, 69999999, 99999999, 399999999, 699999999, 999999999, 3999999999, 6999999999, 9999999999, 39999999999, 69999999999
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
0,2
|
|
|
LINKS
|
|
|
|
FORMULA
|
a(n) = a(n-1)+10*a(n-3)-10*a(n-4). G.f.: 3*x*(x^2+x+1) / ((x-1)*(10*x^3-1)). [Colin Barker, Feb 01 2013]
|
|
|
MATHEMATICA
|
LinearRecurrence[{1, 0, 10, -10}, {0, 3, 6, 9}, 40] (* Harvey P. Dale, Oct 01 2018 *)
|
|
|
PROG
|
(Python)
def a(n): q, r = divmod(3*n, 9); return int(str(r) + "9"*q)
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
nonn,base,easy
|
|
|
AUTHOR
|
|
|
|
STATUS
|
approved
|
| |
|
|
