|
| |
|
|
A061283
|
|
Smallest number with exactly 2n-1 divisors.
|
|
14
|
|
|
|
1, 4, 16, 64, 36, 1024, 4096, 144, 65536, 262144, 576, 4194304, 1296, 900, 268435456, 1073741824, 9216, 5184, 68719476736, 36864, 1099511627776, 4398046511104, 3600, 70368744177664, 46656, 589824, 4503599627370496, 82944
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,2
|
|
|
COMMENTS
|
The terms are always squares (because the divisors of a non-square N come in pairs, d and N/d, and so their number is always even - N. J. A. Sloane, Dec 26 2018).
|
|
|
LINKS
|
T. D. Noe, Table of n, a(n) for n=1..1000 (using A005179)
|
|
|
FORMULA
|
a(n) = Min{k | A000005(k)=2n-1}.
a(p) = 2^(p-1) for prime p.
|
|
|
EXAMPLE
|
for n=15, a(n)=144 with 15 divisors: {1,2,3,4,6,8,9,12...}.
|
|
|
CROSSREFS
|
Cf. A000005, A000290, A005408, A005179, A003680, A016017, A037992, A055079, A048691.
Sequence in context: A162547 A073533 A330689 * A242354 A001264 A307138
Adjacent sequences: A061280 A061281 A061282 * A061284 A061285 A061286
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Labos Elemer, May 22 2001
|
|
|
STATUS
|
approved
|
| |
|
|
