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 A056265 Indices of primes in sequence defined by A(0) = 99, A(n) = 10*A(n-1) - 61 for n > 0. 3
 1, 5, 11, 109, 3607, 37783 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that (830*10^n + 61)/9 is prime. - Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004 Numbers n such that digit 9 followed by n >= 0 occurrences of digit 2 followed by digit 9 is prime. Numbers corresponding to terms <= 3607 are certified primes. For number corresponding to 37783 see P. De Geest, PDP Reference Table. REFERENCES Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. LINKS Patrick De Geest, PDP Reference Table - 929. Makoto Kamada, Prime numbers of the form 922...229. FORMULA a(n) = A082718(n) - 2. EXAMPLE 9222229 is prime, hence 5 is a term. MATHEMATICA Do[If[PrimeQ[(9*10^n + 2*(10^n - 1)/9)*10 + 9], Print[n]], {n, 1, 2500}] Select[Range[2000], PrimeQ[(830 10^# + 61) / 9] &] (* Vincenzo Librandi, Nov 02 2014 *) PROG (PARI) a=99; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-61) \\ Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004 (PARI) for(n=0, 1000, if(isprime((830*10^n + 61)/9), print1(n, ", "))) \\ Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004 (MAGMA) [n: n in [0..1000] | IsPrime((830*10^n + 61) div 9)]; // Vincenzo Librandi, Nov 02 2014 CROSSREFS Cf. A000533, A002275, A068651, A082718. Sequence in context: A075706 A236509 A057178 * A302144 A041909 A041048 Adjacent sequences:  A056262 A056263 A056264 * A056266 A056267 A056268 KEYWORD hard,nonn,more AUTHOR Robert G. Wilson v, Aug 18 2000 EXTENSIONS 3607 from Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004 37783 from Patrick De Geest, Jun 26 2005 Edited by N. J. A. Sloane, Jan 14 2008 Edited by Ray Chandler, Oct 20 2010 Comments section edited by Patrick De Geest, Nov 02 2014 Editied by Ray Chandler, Nov 05 2014 STATUS approved

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Last modified July 17 01:41 EDT 2018. Contains 312693 sequences. (Running on oeis4.)