|
Search: id:A133321
|
|
|
| A133321 |
|
Inserting any (identical) digit between adjacent digits of an odd semiprime k never yields a prime. |
|
+0
1
|
|
| 15, 25, 35, 55, 65, 85, 95, 115, 121, 143, 145, 155, 185, 187, 205, 215, 235, 253, 265, 295, 299, 305, 335, 341, 355, 365, 393, 395, 411, 415, 437, 445, 451, 473, 485, 505, 515, 535, 545, 565, 583, 635, 655, 671, 679, 685, 695, 717, 745, 755, 781, 785, 815
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Odd semiprime analogue of A050805. Trivially true for any digit if we substitute "even semiprime" for "odd semiprime." Trivially true for any semiprime which is a multiple of 5 (A001750). The nonmultiples of 5 in this sequence begin 121, 143, 187, 253, 299, 341.
|
|
EXAMPLE
|
121 is in the sequence because 10201, 11211, 12221, 13231, 14241, 15251, 16261, 17271, 18281, 19291 are all composite.
|
|
CROSSREFS
|
Cf. A001358, A001750, A050674-A050719, A050805, A050806.
Sequence in context: A050693 A152246 A069823 this_sequence A031888 A046291 A020302
Adjacent sequences: A133318 A133319 A133320 this_sequence A133322 A133323 A133324
|
|
KEYWORD
|
base,easy,nonn
|
|
AUTHOR
|
Jonathan Vos Post (jvospost3(AT)gmail.com), Oct 18 2007
|
|
EXTENSIONS
|
More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 22 2007
|
|
|
Search completed in 0.002 seconds
|
