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 A056251 Indices of primes in sequence defined by A(0) = 33, A(n) = 10*A(n-1) - 17 for n > 0. 3
 1, 11, 13, 29, 103, 125, 341, 599, 9823 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that (280*10^n + 17)/9 is prime. Numbers n such that digit 3 followed by n >= 0 occurrences of digit 1 followed by digit 3 is prime. Numbers corresponding to terms <= 599 are certified primes. REFERENCES Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. LINKS Patrick De Geest, PDP Reference Table - 313. Makoto Kamada, Prime numbers of the form 311...113. FORMULA a(n) = A082704(n) - 2. EXAMPLE 313 is prime, hence 1 is a term. MATHEMATICA Flatten[Position[NestList[10#-17&, 33, 600], _?PrimeQ]-1] (* This generates the first 8 terms of the sequence. Changing the last constant from 600 to 9825 will generate all 9 terms of the sequence but it will take a long time to do so. - Harvey P. Dale, May 16 2012 *) Select[Range[0, 2000], PrimeQ[(280 10^# + 17) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *) PROG (PARI) a=33; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-17) (PARI) for(n=0, 1500, if(isprime((280*10^n+17)/9), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A068650, A082704. Sequence in context: A107645 A106014 A261371 * A222805 A089755 A262254 Adjacent sequences:  A056248 A056249 A056250 * A056252 A056253 A056254 KEYWORD nonn,hard,more AUTHOR Robert G. Wilson v, Aug 18 2000 EXTENSIONS Additional comments from Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 20 2004 Edited by N. J. A. Sloane at the suggestion of Andrew Plewe, Jun 15 2007 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 Added and updated the links section, by Patrick De Geest, Nov 02 2014 Edited by Ray Chandler, Nov 04 2014 STATUS approved

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