|
|
A138920
|
|
Indices k such that A020509(k)=Phi[k](-10) is prime, where Phi is a cyclotomic polynomial.
|
|
20
|
|
|
4, 5, 7, 12, 19, 24, 31, 36, 38, 46, 48, 53, 67, 75, 78, 120, 186, 196, 293, 320, 327, 369, 634, 641, 713, 770, 931, 1067, 1172, 1194, 1404, 1452, 1752, 1812, 1836, 1844, 1875, 1890, 2062, 2137, 2177, 2232, 2264, 3011, 3042, 3261, 3341, 4775, 5334, 6685
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
"Unique [period] primes" (A040017) are often of the form Phi[k](10) or Phi[k](-10).
Two cyclotomic polynomial identities tightly connect this sequence to A138940: 1) Phi_2k(x) = Phi_k(-x) for odd integer k > 1. 2) Phi_4k(x) = Phi_2k(x^2) for all positive integer k. - Ray Chandler, Apr 30 2017
|
|
LINKS
|
|
|
MATHEMATICA
|
Select[Range[1000], PrimeQ[Cyclotomic[#, -10]] &]
|
|
PROG
|
(PARI) for( i=1, 999, is/*pseudo*/prime( polcyclo(i, -10)) &&& print1( i", ")) /* for PARI < 2.4.2 use ...subst(polcyclo(i, x), x, -10)... */
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|