|
|
A166565
|
|
Primes p such that product of digits +- 1 is prime.
|
|
1
|
|
|
23, 29, 41, 43, 61, 67, 89, 163, 167, 223, 233, 269, 349, 383, 431, 439, 463, 523, 569, 613, 617, 631, 643, 659, 761, 883, 1123, 1129, 1163, 1213, 1223, 1231, 1237, 1249, 1291, 1321, 1327, 1361, 1429, 1439, 1453, 1459, 1493, 1523, 1543, 1549, 1613, 1621
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
23 is in sequence because 2*3+1=7 and 2*3-1=5; 41 because 4*1+1=5 and 4*1-1=3.
|
|
LINKS
|
|
|
MATHEMATICA
|
Select[Prime[Range[5000]], PrimeQ[Times@@IntegerDigits[#] - 1] && PrimeQ[Times@@IntegerDigits[#] + 1] &] (* Vincenzo Librandi, Feb 15 2014 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
|
|
EXTENSIONS
|
Corrected (29 inserted) and extended beyond 659 by R. J. Mathar, Nov 30 2009
|
|
STATUS
|
approved
|
|
|
|