OFFSET
1,2
COMMENTS
Numbers n such that (370*10^n + 71)/9 is prime.
Numbers n such that digit 4 followed by n >= 0 occurrences of digit 1 followed by digit 9 is prime.
a(10) > 10^5. - Robert Price, Apr 14 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A102983(n) - 1.
EXAMPLE
411119 is prime, hence 4 is a term.
MATHEMATICA
Select[Range[0, 2000], PrimeQ[(370*10^# + 71)/9] &] (* Robert Price, Apr 14 2015 *)
PROG
(PARI) a=49; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-71)
(PARI) for(n=0, 1500, if(isprime((370*10^n+71)/9), print1(n, ", ")))
(Magma) [n: n in [0..300] | IsPrime((370*10^n+71) div 9)]; // Vincenzo Librandi, Apr 15 2015
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 14 2004
EXTENSIONS
3886 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(7)-a(9) derived from A102983 by Robert Price, Apr 14 2015
STATUS
approved