OFFSET
1,2
COMMENTS
Numbers n such that (280*10^n + 17)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 1 followed by digit 3 is prime.
Numbers corresponding to terms <= 599 are certified primes.
All terms are odd since 11 is the only palindromic prime with an even number of digits. - Chai Wah Wu, Nov 05 2019
a(10) > 2*10^5. - Tyler Busby, Feb 01 2023
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
Patrick De Geest, PDP Reference Table - 313.
Makoto Kamada, Prime numbers of the form 311...113.
FORMULA
a(n) = A082704(n) - 2.
EXAMPLE
313 is prime, hence 1 is a term.
MATHEMATICA
Flatten[Position[NestList[10#-17&, 33, 600], _?PrimeQ]-1] (* This generates the first 8 terms of the sequence. Changing the last constant from 600 to 9825 will generate all 9 terms of the sequence but it will take a long time to do so. - Harvey P. Dale, May 16 2012 *)
Select[Range[0, 2000], PrimeQ[(280 10^# + 17) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *)
PROG
(PARI) a=33; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-17)
(PARI) for(n=0, 1500, if(isprime((280*10^n+17)/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 20 2004
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Jun 15 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Added and updated the links section, by Patrick De Geest, Nov 02 2014
Edited by Ray Chandler, Nov 04 2014
STATUS
approved