OFFSET
1,3
COMMENTS
Numbers n such that 60*10^n + 1 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 0 followed by digit 1 is prime.
Numbers corresponding to terms <= 838 are certified primes.
Certified primality of numbers corresponding to terms 1008,1018,1172,1333 with Primo. - Ryan Propper, Jun 20 2005
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
Makoto Kamada, Prime numbers of the form 600...001.
FORMULA
a(n) = A056805(n+1) - 1.
EXAMPLE
600000001 is prime, hence 7 is a term.
PROG
(PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-9)
(PARI) for(n=0, 1500, if(isprime(60*10^n+1), 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) and Stefan Steinerberger, Apr 28 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
a(26)-a(28) from Kamada data by Ray Chandler, Apr 23 2015
STATUS
approved