|
| |
|
|
A053181
|
|
Composite numbers ending in 9.
|
|
0
| |
|
|
9, 39, 49, 69, 99, 119, 129, 159, 169, 189, 209, 219, 249, 259, 279, 289, 299, 309, 319, 329, 339, 369, 399, 429, 459, 469, 489, 519, 529, 539, 549, 559, 579, 589, 609, 629, 639, 649, 669, 679, 689, 699, 729, 749, 759, 779, 789, 799, 819, 849, 869, 879, 889, 899
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| Numbers of the form 10n + 9 (A017377) not in A030433. Obviously multiples of 2 or 5 can't be in A017377 nor this sequence. All other primes occur as factors of these terms infinitely often. For example: If n is a multiple of 3, then 10n + 9 is in this sequence; if n = 4 mod 7, then 10n + 9 is in this sequence; if n = 9 mod 11, then 10n + 9 is in this sequence; and so on and so forth. The first of these congruences to be satisfied determines the least prime factor of 10n + 9. - From Alonso del Arte, Jun 23 2011
|
|
|
FORMULA
| a(n) ~ 10n. [Charles R Greathouse IV, Jun 24 2011]
|
|
|
MATHEMATICA
| Complement[Range[9, 1000, 10], Prime[Range[PrimePi[1000]]]] (* From Alonso del Arte, Jun 23 2011 *)
|
|
|
PROG
| (PARI) forstep(n=9, 1e3, 10, if(!isprime(n), print1(n", "))) \\ Charles R Greathouse IV, Jun 24 2011
|
|
|
CROSSREFS
| Sequence in context: A071229 A071238 A050854 * A192608 A158447 A023163
Adjacent sequences: A053178 A053179 A053180 * A053182 A053183 A053184
|
|
|
KEYWORD
| easy,nonn,base
|
|
|
AUTHOR
| Enoch Haga (Enokh(AT)comcast.net), Feb 29 2000
|
|
|
EXTENSIONS
| 9 added by Kausthub Gudipati (shivakausthub(AT)yahoo.com), Jun 16 2011
|
| |
|
|
