A102031 Indices of primes in sequence defined by A(0) = 19, A(n) = 10*A(n-1) - 1 for n > 0.
0, 2, 11, 266, 842, 6299, 37991, 54116, 121241, 121620
Offset: 1
Examples
1889 is prime, hence 2 is a term.
References
- Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
Links
Programs
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Magma
[n: n in [0..300] | IsPrime((170*10^n+1) div 9)]; // Vincenzo Librandi, Nov 17 2014
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Maple
A102031:=n->`if`(isprime((170*10^n+1)/9), n, NULL): seq(A102031(n), n=0..10^3); # Wesley Ivan Hurt, Nov 16 2014
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Mathematica
Select[Range[0, 10^3], PrimeQ[(170*10^# + 1)/9] &] (* Wesley Ivan Hurt, Nov 16 2014 *)
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PARI
a=19;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-1)
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PARI
for(n=0,1500,if(isprime((170*10^n+1)/9),print1(n,",")))
Formula
a(n) = A102945(n) - 1.
Extensions
6299 from Herman Jamke (hermanjamke(AT)fastmail.fm), Dec 22 2007
a(7)-a(10) added by Max Alekseyev, Dec 12 2011
Comments