OFFSET
1,2
COMMENTS
Numbers n such that (320*10^n - 23)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 5 followed by digit 3 is prime.
Numbers corresponding to terms <= 1973 are certified primes. For larger numbers see P. De Geest, PDP Reference Table.
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
Patrick De Geest, PDP Reference Table - 353.
Makoto Kamada, Prime numbers of the form 355...553.
FORMULA
a(n) = A082707(n) - 2.
EXAMPLE
353 is prime, hence 1 is a term.
MATHEMATICA
Select[Range[0, 2000], PrimeQ[(320 10^# - 23) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *)
PROG
(PARI) a=33; for(n=0, 2000, if(isprime(a), print1(n, ", ")); a=10*a+23)
(PARI) for(n=0, 2000, if(isprime((320*10^n-23)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Robert G. Wilson v, Aug 18 2000
EXTENSIONS
Additional comments from Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, May 31 2007, Jun 15 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Comments section and a link updated by Patrick De Geest, Nov 02 2014
Edited by Ray Chandler, Nov 05 2014
STATUS
approved