OFFSET
1,2
COMMENTS
Numbers n such that (610*10^n - 43)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 7 followed by digit 3 is prime.
Some of the larger entries may only correspond to probable primes.
a(10) > 10^5. - Robert Price, Sep 12 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A103042(n+1) - 1.
EXAMPLE
673 is prime, hence 1 is a term.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(610*10^# - 43)/9] &] (* Robert Price, Sep 12 2015 *)
PROG
(PARI) a=63; for(n=0, 2000, if(isprime(a), print1(n, ", ")); a=10*a+43)
(PARI) for(n=0, 2000, if(isprime((610*10^n-43)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(7)-a(8) from Kamada data by Ray Chandler, Apr 30 2015
a(9) from Robert Price, Sep 12 2015
STATUS
approved