OFFSET
1,3
COMMENTS
Numbers n such that (280*10^n + 53)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime.
Numbers corresponding to terms <= 691 are certified primes.
REFERENCES
Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
LINKS
FORMULA
a(n) = A101393(n) - 1.
EXAMPLE
317 is prime, hence 1 is a term.
MATHEMATICA
nn=2900; Transpose[Select[Thread[{NestList[10#-53&, 37, nn], Range[0, nn]}], PrimeQ[First[#]]&]] [[2]] (* Harvey P. Dale, Mar 26 2011 *)
PROG
(PARI) a=37; for(n=0, 2000, if(isprime(a), print1(n, ", ")); a=10*a-53)
(PARI) for(n=0, 2000, if(isprime((280*10^n+53)/9), print1(n, ", ")))
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(8) derived from A101393 by Robert Price, Jan 26 2015
STATUS
approved