|
Search: id:A089374
|
|
|
| A089374 |
|
Numbers n such that the concatenation (in descending order) of all the divisors of n, with 1 in the least significant position, is prime. |
|
+0
2
|
|
| 3, 4, 7, 13, 19, 25, 31, 39, 43, 48, 91, 97, 103, 109, 117, 151, 157, 181, 193, 211, 241, 244, 247, 271, 289, 292, 301, 309, 325, 337, 349, 367, 388, 409, 421, 439, 487, 523, 547, 571, 597, 601, 613, 628, 631, 633, 687, 691, 703, 711, 733, 769, 772, 793, 811
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
EXAMPLE
|
4 is a term as 421 is prime; 39 is a term as concatenation of 39,13,3 and 1, i.e. 391331, is prime.
25 is a member as 2551 is prime.
48 is a member as 48241612864321 is a prime.
|
|
MAPLE
|
select(n->isprime(parse(cat("", op(sort([op(numtheory[divisors](n))], `>`))))), [$1..3000])[]; (Alec Mihailovs, Aug 14 2005)
|
|
CROSSREFS
|
Cf. A069582.
Sequence in context: A088764 A093124 A055664 this_sequence A029552 A125118 A116201
Adjacent sequences: A089371 A089372 A089373 this_sequence A089375 A089376 A089377
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 08 2003
|
|
EXTENSIONS
|
Corrected and extended by David Wasserman (wasserma(AT)spawar.navy.mil), Sep 15 2005
Edited by N. J. A. Sloane (njas(AT)research.att.com), Apr 29 2007
|
|
|
Search completed in 0.002 seconds
|
