

A158725


Nonrepdigit 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
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OFFSET

1,1


COMMENTS

Nonrepdigit 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 A157342 A230226
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



