|
| |
|
|
A125875
|
|
Odd numbers n such that cos(2pi/n) is an algebraic number of a 13-smooth degree, but not 11-smooth.
|
|
2
|
|
|
|
53, 79, 131, 157, 159, 169, 237, 265, 313, 371, 393, 395, 471, 477, 507, 521, 547, 553, 583, 655, 677, 689, 711, 785, 795, 845, 859, 869, 901, 911, 917, 937, 939, 1007, 1027, 1093, 1099, 1113, 1171, 1179, 1183, 1185, 1219, 1249, 1301, 1325, 1343
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
A regular polygon of a(n) sides can be constructed if one also has an angle trisector, 5-, 7-, 11- and 13-sector.
|
|
|
LINKS
|
Table of n, a(n) for n=1..47.
|
|
|
MATHEMATICA
|
Do[If[Take[FactorInteger[EulerPhi[2n+1]][[ -1]], 1]=={13}, Print[2n+1]], {n, 1, 10000}]
|
|
|
CROSSREFS
|
Cf. A125866-A125878.
Sequence in context: A043992 A032421 A129257 * A059245 A268753 A125876
Adjacent sequences: A125872 A125873 A125874 * A125876 A125877 A125878
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Artur Jasinski, Dec 13 2006
|
|
|
EXTENSIONS
|
Edited by Don Reble, Apr 24 2007
|
|
|
STATUS
|
approved
|
| |
|
|
