|
| |
|
|
A056250
|
|
Indices of primes in sequence defined by A(0) = 11, A(n) = 10*A(n-1) + 81 for n > 0.
|
|
1
|
|
|
|
0, 1, 3, 7, 39, 85, 199, 729, 1459, 23671, 28629
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,3
|
|
|
COMMENTS
|
Numbers n such that (180*10^n - 81)/9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 9 followed by digit 1 is prime.
Numbers corresponding to terms <= 729 are certified primes. For number corresponding to 1459 see P. De Geest, PDP Reference Table.
a(n) = A082703(n-2) - 2 for n > 1.
|
|
|
REFERENCES
|
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
|
|
|
LINKS
|
Table of n, a(n) for n=1..11.
P. De Geest, PDP Reference Table
Makoto Kamada, Factorizations of 199...991.
|
|
|
EXAMPLE
|
191 is prime, hence 1 is a term.
|
|
|
PROG
|
(PARI) a=11; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+81)
(PARI) for(n=0, 1500, if(isprime((180*10^n-81)/9), print1(n, ", ")))
|
|
|
CROSSREFS
|
Cf. A000533, A002275, A082703.
Sequence in context: A192198 A061931 A057203 * A113870 A209326 A074582
Adjacent sequences: A056247 A056248 A056249 * A056251 A056252 A056253
|
|
|
KEYWORD
|
nonn,hard,more
|
|
|
AUTHOR
|
Robert G. Wilson v, Aug 18 2000
|
|
|
EXTENSIONS
|
Additional comments from Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004
Edited by N. J. A. Sloane, Jun 15 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
|
|
|
STATUS
|
approved
|
| |
|
|
