OFFSET
1,2
COMMENTS
Numbers n such that (730*10^n + 17)/9 is prime.
Numbers n such that digit 8 followed by n >= 0 occurrences of digit 1 followed by digit 3 is prime.
Numbers corresponding to terms <= 744 are certified primes.
a(15) > 10^5. - Robert Price, Oct 16 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A103071(n) - 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
EXAMPLE
81111111113 is prime, hence 9 is a term.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(730*10^# + 17)/9] &] (* Robert Price, Oct 16 2015 *)
PROG
(PARI) a=83; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-17)
(PARI) for(n=0, 1000, if(isprime((730*10^n+17)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 30 2004
EXTENSIONS
7752 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(7)-a(11) from Kamada data by Ray Chandler, Apr 29 2015
a(12)-a(14) from Robert Price, Oct 16 2015
STATUS
approved