|
|
A182686
|
|
a(n) = the largest n-digit number with exactly 13 divisors, a(n) = 0 if no such number exists.
|
|
2
|
|
|
0, 0, 0, 4096, 0, 531441, 0, 0, 244140625, 0, 13841287201, 0, 3138428376721, 23298085122481, 582622237229761, 2213314919066161, 21914624432020321, 787662783788549761, 6582952005840035281, 39959630797262576401
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,4
|
|
COMMENTS
|
a(n) = the largest n-digit number of the form p^12 (p = prime), a(n) = 0 if no such number exists.
|
|
LINKS
|
|
|
FORMULA
|
|
|
MAPLE
|
f:= proc(n) local r;
r:= prevprime(ceil(10^(n/12)))^12;
if r < 10^(n-1) then 0 else r fi;
end proc:
f(1):= 0: f(2):= 0: f(3):=0:
|
|
PROG
|
(PARI) a(n) = my(r=precprime(ceil(10^(n/12))-1)^12); if(r < 10^(n-1), return(0)); r \\ Adapted from Robert Israel's Maple program; Felix Fröhlich, Apr 03 2019
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|