OFFSET
1,2
COMMENTS
Numbers n such that 30*10^n + 1 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 0 followed by digit 1 is prime.
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 300...001.
FORMULA
a(n) = A056807(n) - 1.
EXAMPLE
3001 is prime, hence 2 is a term.
PROG
(PARI) a=31; for(n=0, 2000, if(isprime(a), print1(n, ", ")); a=10*a-9)
(PARI) for(n=0, 2000, if(isprime(30*10^n+1), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004
EXTENSIONS
More terms from Kamada link by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(18) from Roman Makarchuk, Dec 05 2008 confirmed as next term by Ray Chandler, Mar 02 2012
a(19) from Alexander Gramolin, Feb 24 2012 confirmed as next term by Ray Chandler, Mar 02 2012
a(20)-a(21) derived from A056807 by Robert Price, Jan 26 2015
STATUS
approved