OFFSET
1,2
COMMENTS
Numbers n such that (320*10^n + 13)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 5 followed by digit 7 is prime.
a(16) > 10^5. - Robert Price, Apr 07 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A102972(n+1) - 1.
EXAMPLE
3557 is prime, hence 2 is a term.
MATHEMATICA
Select[Range[0, 10000], PrimeQ[(320*10^# + 13)/9] &] (* Robert Price, Apr 07 2015 *)
PROG
(PARI) a=37; for(n=0, 2000, if(isprime(a), print1(n, ", ")); a=10*a-13)
(PARI) for(n=0, 2000, if(isprime((320*10^n+13)/9), print1(n, ", ")))
(Magma) [n: n in [0..1000] | IsPrime((320*10^n+13) div 9)]; // Vincenzo Librandi, Apr 08 2015
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004
EXTENSIONS
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(11)-a(15) derived from A102972 by Robert Price, Apr 07 2015
STATUS
approved