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 A056253 Indices of primes in sequence defined by A(0) = 33, A(n) = 10*A(n-1) + 13 for n > 0. 2
 5, 11, 491, 5567, 24755 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers n such that (310*10^n - 13)/9 is prime. Numbers n such that digit 3 followed by n >= 0 occurrences of digit 4 followed by digit 3 is prime. Numbers corresponding to terms <= 491 are certified primes. For larger numbers see P. De Geest, PDP Reference Table. a(4) = 5567 is based on A082706. REFERENCES Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. LINKS Patrick De Geest, PDP Reference Table - 343. Makoto Kamada, Prime numbers of the form 344...443. FORMULA a(n) = A082706(n) - 2. EXAMPLE 3444443 is prime, hence 5 is a term. MATHEMATICA Select[Range[0, 2000], PrimeQ[(310 10^# -13) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *) PROG (PARI) a=33; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+13) (PARI) for(n=0, 1500, if(isprime((310*10^n-13)/9), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A082706. Sequence in context: A228054 A283354 A156330 * A101832 A046957 A174957 Adjacent sequences:  A056250 A056251 A056252 * A056254 A056255 A056256 KEYWORD nonn,hard,more,changed AUTHOR Robert G. Wilson v, Aug 18 2000 EXTENSIONS 24755 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 Comments section and a link edited by Patrick De Geest, Nov 02 2014 Edited by Ray Chandler, Nov 05 2014 STATUS approved

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Last modified January 18 05:30 EST 2019. Contains 319269 sequences. (Running on oeis4.)