OFFSET
1,2
COMMENTS
Numbers n such that (760*10^n - 13)/9 is a prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 4 followed by digit 3 is prime.
Numbers corresponding to terms <= 441 are certified primes.
a(19) > 10^5. - Robert Price, Oct 20 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A103080(n+1) - 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008; adapted to offset by Robert Price, Oct 21 2015
EXAMPLE
84443 is prime, hence 3 is a term.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(760*10^# - 13)/9] &] (* Robert Price, Oct 20 2015 *)
PROG
(PARI) a=83; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+13)
(PARI) for(n=0, 1500, if(isprime((760*10^n-13)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 30 2004
EXTENSIONS
5 more terms from Ryan Propper, Jun 18 2005
a(18) from Kamada data by Ray Chandler, Apr 29 2015
STATUS
approved