|
| |
|
|
A102946
|
|
Numbers n such that 2*10^n-7 is prime.
|
|
2
|
|
|
|
1, 2, 3, 4, 6, 16, 21, 28, 48, 82, 122, 130, 282, 304, 4602, 12984, 13614, 42762, 90597
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,2
|
|
|
COMMENTS
|
Also numbers n such that 10^n + 9*R_n - 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
|
|
|
LINKS
|
Table of n, a(n) for n=1..19.
Makoto Kamada, Factorizations of 199...993.
Index entries for primes involving repunits.
|
|
|
MATHEMATICA
|
Do[ If[ PrimeQ[2*10^n - 7], Print[n]], {n, 0, 10000}]
|
|
|
CROSSREFS
|
Sequence in context: A204540 A002087 A049288 * A026094 A069860 A084391
Adjacent sequences: A102943 A102944 A102945 * A102947 A102948 A102949
|
|
|
KEYWORD
|
more,nonn
|
|
|
AUTHOR
|
Robert G. Wilson v, Dec 16 2004
|
|
|
EXTENSIONS
|
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Addition of a(18)-a(19) from Kamada data by Robert Price, Dec 10 2010
|
|
|
STATUS
|
approved
|
| |
|
|
