A056254 Indices of primes in sequence defined by A(0) = 33, A(n) = 10*A(n-1) + 23 for n > 0.
1, 7, 139, 229, 425, 461, 725, 1973, 7229, 45859, 47303
Offset: 1
Examples
353 is prime, hence 1 is a term.
References
- Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
Links
- Patrick De Geest, PDP Reference Table - 353.
- Makoto Kamada, Prime numbers of the form 355...553.
- Index entries for primes involving repunits.
Programs
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Mathematica
Select[Range[0, 2000], PrimeQ[(320 10^# - 23) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *)
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PARI
a=33;for(n=0,2000,if(isprime(a),print1(n,","));a=10*a+23)
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PARI
for(n=0,2000,if(isprime((320*10^n-23)/9),print1(n,",")))
Formula
a(n) = A082707(n) - 2.
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 S. Plewe, May 31 2007, Jun 15 2007
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Comments section and a link updated by Patrick De Geest, Nov 02 2014
Edited by Ray Chandler, Nov 05 2014
Comments