OFFSET
1,1
COMMENTS
Numbers n such that (530*10^n - 71)/9 is prime.
Numbers n such that digit 5 followed by n >= 0 occurrences of digit 8 followed by digit 1 is prime.
Numbers corresponding to terms <= 857 are certified primes.
a(15) > 10^5. - Robert Price, Sep 08 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A103022(n) - 1.
EXAMPLE
5881 is prime, hence 2 is a term.
MATHEMATICA
Select[Range[0, 300], PrimeQ[(530*10^# - 71)/9] &] (* Robert Price, Sep 08 2015 *)
PROG
(PARI) a=51; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+71)
(PARI) for(n=0, 1500, if(isprime((530*10^n-71)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004
EXTENSIONS
1688 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(11)-a(13) from Kamada data by Ray Chandler, Apr 30 2015
a(14) from Robert Price, Sep 08 2015
STATUS
approved