OFFSET
1,3
COMMENTS
Numbers n such that (120*10^n + 33)/9 is prime.
Numbers n such that digit 1 followed by n >= 0 occurrences of digit 3 followed by digit 7 is prime.
Numbers corresponding to terms <= 886 are certified primes.
Next term after 7683 is greater than 10000. - Ryan Propper, Jul 01 2005
a(21) > 10^5. - Robert Price, Nov 15 2014
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A102932(n+1) - 1. - Robert Price, Nov 15 2014
EXAMPLE
137 is prime, hence 1 is a term.
PROG
(PARI) a=17; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-33)
(PARI) for(n=0, 1500, if(isprime((120*10^n+33)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004
EXTENSIONS
6 more terms, corresponding to probable primes, from Ryan Propper, Jul 01 2005
Edited by T. D. Noe, Oct 30 2008
a(18)-a(20) derived from A102932 by Robert Price, Nov 15 2014
STATUS
approved