OFFSET
1,2
COMMENTS
Numbers n such that (440*10^n - 71)/9 is prime.
Numbers n such that digit 4 followed by n >= 0 occurrences of digit 8 followed by digit 1 is prime.
Number corresponding to term 462 is a certified prime. No further terms up to 5000.
a(3) > 2*10^5. - Robert Price, Oct 15 2015
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A102997(n) - 1.
EXAMPLE
41 is prime, hence 0 is a term.
PROG
(PARI) a=41; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+71)
(PARI) for(n=0, 1500, if(isprime((440*10^n-71)/9), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn,bref,hard,more
AUTHOR
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 14 2004
STATUS
approved