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 A250187 Numbers n such that Phi(38,n) is prime, where Phi is the cyclotomic polynomial. 18
 2, 10, 13, 24, 28, 43, 47, 49, 54, 65, 83, 98, 106, 143, 152, 177, 184, 190, 194, 195, 241, 249, 259, 264, 292, 315, 319, 345, 353, 355, 386, 394, 481, 500, 517, 525, 534, 535, 556, 595, 601, 649, 656, 680, 686, 687, 697, 707, 710, 756, 798, 804, 817, 818, 829, 839, 841, 858, 864, 891, 906, 912, 932, 948, 973, 991, 994, 1012 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS G. C. Greubel, Table of n, a(n) for n = 1..10000 MATHEMATICA Select[Range[2000], PrimeQ[(#^19 + 1) / (# + 1)] &] (* Vincenzo Librandi, Jan 15 2015 *) PROG (MAGMA) [n: n in [1..2000]| IsPrime((n^19+1) div (n+1))]; // Vincenzo Librandi, Jan 15 2015 (PARI) select(x->isprime(x), vector(1000, n, polcyclo(38, n)), 1) \\ Michel Marcus, Jan 15 2015 CROSSREFS Cf. A246392. Sequence in context: A058216 A297998 A037386 * A062317 A140510 A277087 Adjacent sequences:  A250184 A250185 A250186 * A250188 A250189 A250190 KEYWORD nonn AUTHOR R. J. Mathar, Jan 12 2015 STATUS approved

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Last modified July 23 21:46 EDT 2021. Contains 346265 sequences. (Running on oeis4.)