OFFSET
1,2
COMMENTS
Numbers n such that (370*10^n + 17)/9 is prime.
Numbers n such that digit 4 followed by n >= 0 occurrences of digit 1 followed by digit 3 is prime.
Numbers corresponding to terms <= 228 are certified primes.
a(20) > 10^5. - Robert Price, May 08 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A102981(n) - 1.
EXAMPLE
41113 is prime, hence 3 is a term.
MATHEMATICA
Select[Range[0, 300], PrimeQ[(370*10^# + 17)/9] &] (* Robert Price, May 08 2015 *)
PROG
(PARI) a=43; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-17)
(PARI) for(n=0, 1500, if(isprime((370*10^n+17)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 14 2004
EXTENSIONS
9438 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(17)-a(19) from Kamada data by Ray Chandler, Apr 30 2015
STATUS
approved