A056260 Indices of primes in sequence defined by A(0) = 77, A(n) = 10*A(n-1) - 3 for n > 0. Numbers n such that (690*10^n + 3)/9 is prime.
3, 5, 53, 95, 453, 573, 3383, 11439, 12623, 19445, 35459, 81213, 95325
Offset: 1
Examples
76667 is prime, hence 3 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 - 767.
- Makoto Kamada, Prime numbers of the form 766...667.
Programs
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Magma
[n: n in [0..300] | IsPrime((690*10^n+3) div 9)]; // Vincenzo Librandi, Nov 03 2014
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Mathematica
Select[Range[3500], PrimeQ[(690 10^# + 3) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *)
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PARI
a=77;for(n=0,1000,if(isprime(a),print1(n,","));a=10*a-3)
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PARI
for(n=0,1000,if(isprime((690*10^n+3)/9),print1(n,",")))
Formula
a(n) = A082714(n) - 2.
Extensions
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Apr 29 2007, Jun 15 2007
a(7)-a(11) from Robert G. Wilson v, May 02 2007
Two more terms added from PDP Table, a link added and comments section updated by Patrick De Geest, Nov 02 2014
Edited by Ray Chandler, Nov 05 2014
Comments