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 A158725 Non-repdigit composite numbers not divisible by 2, 3, 5 or 11. 3
 49, 91, 119, 133, 161, 169, 203, 217, 221, 247, 259, 287, 289, 299, 301, 323, 329, 343, 361, 371, 377, 391, 403, 413, 427, 437, 469, 481, 493, 497, 511, 527, 529, 533, 551, 553, 559, 581, 589, 611, 623, 629, 637, 667, 679, 689, 697, 703, 707, 713, 721, 731 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Non-repdigit composite numbers ending in 1, 3, 7 or 9, with digital root not a multiple of 3 and whose alternate digit sums do not differ by a multiple of 11. The "compositeness" of larger entries of the sequence is not obvious right away or deducible by mere inspection, and hence these terms readily lend themselves to be (erroneously) suspected as primes to the casual glance. This differs from the corresponding sequence without the repunit condition starting at a(1351) = 11123 rather than 11111. - Charles R Greathouse IV, Sep 08 2012 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 FORMULA a(n) ~ kn with k = 33/8. - Charles R Greathouse IV, Sep 08 2012 PROG (PARI) is(n)=gcd(n, 330)==1&&!isprime(n)&&n%(10^#Str(n)\9) \\ Charles R Greathouse IV, Sep 08 2012 CROSSREFS Cf. A007775, A053795, A008364. Sequence in context: A273937 A326257 A231275 * A090825 A350704 A157342 Adjacent sequences: A158722 A158723 A158724 * A158726 A158727 A158728 KEYWORD nonn AUTHOR Lekraj Beedassy, Mar 24 2009 EXTENSIONS Corrected and extended by Ray Chandler, Mar 27 2009 STATUS approved

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Last modified July 13 23:31 EDT 2024. Contains 374290 sequences. (Running on oeis4.)