|
Search: id:A056655
|
|
|
| A056655 |
|
Numbers n such that 10*R_n +7 is prime, where R_n = 11...1 is the repunit (A002275) of length n. |
|
+0
3
|
|
| 0, 1, 3, 4, 7, 22, 28, 39, 130, 135, 214, 610, 766, 2152, 2575
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
COMMENT
|
Also numbers n such that (10^(n+1)+53)/9 is prime.
2575 also produces a probable prime.
|
|
LINKS
|
Index entries for primes involving repunits
|
|
FORMULA
|
a(n) = A097684(n) - 1 for all n >= 0. - Rick L. Shepherd (rshepherd2(AT)hotmail.com), Aug 23 2004
|
|
MATHEMATICA
|
Do[ m = n; If[ primeQ[ 10*(10^n - 1)/9 + 7 ], Print[ n ] ], {n, 1, 1250} ]
|
|
CROSSREFS
|
Cf. A093139 (corresponding primes).
Cf. A097684.
Sequence in context: A113534 A030724 A124082 this_sequence A145593 A042037 A041091
Adjacent sequences: A056652 A056653 A056654 this_sequence A056656 A056657 A056658
|
|
KEYWORD
|
hard,nonn
|
|
AUTHOR
|
Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 09 2000
|
|
EXTENSIONS
|
2152 (giving a probable prime) from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Mar 23 2004
2575 from Rick L. Shepherd (rshepherd2(AT)hotmail.com), Aug 23 2004
|
|
|
Search completed in 0.002 seconds
|
