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 A064507 Numbers of more than one digit that yield primes when cast in their own base. 2
 21, 27, 29, 61, 67, 111, 151, 191, 201, 203, 223, 241, 313, 319, 331, 351, 373, 397, 403, 409, 461, 463, 481, 553, 559, 571, 667, 711, 791, 807, 841, 869, 889, 931, 979, 1071, 1079, 1107, 1129, 1189, 1257, 1273, 1277, 1297, 1431, 1437, 1583, 1611, 1639 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS All terms are coprime to 10. - Robert Israel, Dec 04 2016 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE E.g. 21 in base 21 is 2*21+1=43, 111 is 1*111*111+1*111+1=12433, etc. MAPLE filter:= proc(n) local L, i;    L:= convert(n, base, 10);    isprime(add(L[i]*n^(i-1), i=1..nops(L))) end proc: select(filter, [seq(i, i=11..2000, 2)]); # Robert Israel, Dec 04 2016 PROG (PARI) isok(n) = (n>=10) && isprime(fromdigits(digits(n), n)); \\ Michel Marcus, Dec 04 2016 CROSSREFS Cf. A064508.  Contained in A054684. Sequence in context: A299594 A318544 A173836 * A249729 A280107 A264102 Adjacent sequences:  A064504 A064505 A064506 * A064508 A064509 A064510 KEYWORD nonn,base AUTHOR Jon Perry, Oct 06 2001 EXTENSIONS Offset corrected by Arkadiusz Wesolowski, Oct 19 2013 Name corrected by Robert Israel, Dec 04 2016 STATUS approved

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Last modified October 18 10:25 EDT 2019. Contains 328146 sequences. (Running on oeis4.)