|
| |
|
|
A146309
|
|
a(n) = indices where primes occured in A146306.
|
|
2
| |
|
|
1, 3, 10, 14, 18, 22, 26, 30, 34, 38, 42, 46, 58, 62, 66, 74, 78, 82, 86, 94, 102, 106, 114, 118, 122, 134, 138, 142, 146, 158, 166, 174, 178, 186, 194, 202, 206, 214, 218, 222, 226, 246, 254, 258, 262, 274, 278, 282, 298, 302, 314, 318, 326, 334, 346, 354, 358
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,2
|
|
|
COMMENTS
| General formula (*Artur Jasinski*):
2 Cos[2*Pi/n] = Hypergeometric2F1[(n-6)/(2n),(n+6)/(2n),1/2,3/4] =
Hypergeometric2F1[A146306(n)/A146307(n),A146306(n+12)/A146307(n),1/2,3/4].
2 Cos[2*Pi/n] is root of polynomial of degree = EulerPhi[n]/2 = A000010(n)/2 = A023022(n).
|
|
|
MATHEMATICA
| aa = {}; Do[k = Denominator[(n - 6)/(2 n)]; If[PrimeQ[k], AppendTo[aa, n]], {n, 1, 1000}]; aa (*Artur Jasinski*)
|
|
|
CROSSREFS
| A007310, A051724, A146306, A146307, A146308.
Sequence in context: A041865 A085776 A190706 * A085726 A063796 A063221
Adjacent sequences: A146306 A146307 A146308 * A146310 A146311 A146312
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Artur Jasinski (grafix(AT)csl.pl), Oct 29 2008
|
| |
|
|
