A101731 Indices of primes in sequence defined by A(0) = 47, A(n) = 10*A(n-1) - 3 for n > 0.
0, 1, 5, 9, 11, 12, 21, 31, 45, 60, 67, 89, 109, 651, 1607, 1903, 2002, 3037, 3085, 9579, 9697, 10638, 14460
Offset: 1
Examples
467 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
Programs
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Magma
[n: n in [0..500] | IsPrime((420*10^n+3) div 9)]; // Vincenzo Librandi, Jul 12 2015
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Mathematica
Select[Range[0, 100], PrimeQ[(420 10^# + 3)/9] &] (* Vincenzo Librandi, Jul 12 2015 *)
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PARI
a=47;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-3)
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PARI
for(n=0,1500,if(isprime((420*10^n+3)/9),print1(n,",")))
Formula
a(n) = A099017(n+1) - 1.
Extensions
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(22)-a(23) from Kamada data by Ray Chandler, Apr 30 2015
Comments