OFFSET
1,3
COMMENTS
Numbers n such that (170*10^n - 71)/9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 8 followed by digit 1 is prime.
Numbers corresponding to terms <= 883 are certified primes.
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
Patrick De Geest, PDP Reference Table - 181.
Makoto Kamada, Prime numbers of the form 188...881.
FORMULA
a(n) = A082702(n-1) - 2 for n > 1.
EXAMPLE
181 is prime, hence 1 is a term.
MATHEMATICA
Select[Range[0, 2000], PrimeQ[(170 10^# - 71) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *)
PROG
(PARI) a=11; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+71)
(PARI) for(n=0, 1500, if(isprime((170*10^n-71)/9), print1(n, ", ")))
CROSSREFS
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
Updated and added a link, by Patrick De Geest, Nov 02 2014
Edited by Ray Chandler, Nov 04 2014
STATUS
approved