OFFSET
1,2
COMMENTS
Numbers n such that (490*10^n - 13)/9 is prime.
Numbers n such that digit 5 followed by n >= 0 occurrences of digit 4 followed by digit 3 is prime.
Numbers corresponding to terms <= 794 are certified primes.
a(14) > 10^5. - Robert Price, Jul 16 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A103014(n) - 1.
EXAMPLE
54443 is prime, hence 3 is a term.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(490*10^#-13)/9]&]
PROG
(PARI) a=53; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a+13)
(PARI) for(n=0, 1000, if(isprime((490*10^n-13)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(13) from Robert Price, Jul 16 2015
STATUS
approved