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 A040987 Primes p such that x^5 = 21 has no solution mod p. 2
 31, 41, 71, 101, 131, 151, 181, 191, 211, 241, 251, 271, 281, 311, 331, 401, 431, 491, 521, 541, 571, 701, 751, 761, 811, 821, 881, 911, 941, 971, 991, 1021, 1031, 1051, 1061, 1091, 1151, 1181, 1201, 1291, 1301, 1321, 1361, 1381, 1471 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Complement of A040986 relative to A000040. - Vincenzo Librandi, Sep 19 2012 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MATHEMATICA ok[p_] := Reduce[Mod[x^5 - 21, p] == 0, x, Integers] == False; Select[Prime[Range[300]], ok] (* Vincenzo Librandi, Sep 19 2012  *) PROG (MAGMA) [p: p in PrimesUpTo(1500) | not exists{x: x in ResidueClassRing(p) | x^5 eq 21}]; // Vincenzo Librandi, Sep 19 2012 CROSSREFS Sequence in context: A141180 A176371 A284531 * A040180 A158754 A140458 Adjacent sequences:  A040984 A040985 A040986 * A040988 A040989 A040990 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified September 16 08:53 EDT 2019. Contains 327092 sequences. (Running on oeis4.)