A101840 Indices of primes in sequence defined by A(0) = 37, A(n) = 10*A(n-1) - 3 for n > 0.
0, 1, 11, 14, 50, 193, 497, 2135, 2821, 3761, 7427, 22739, 30451, 37951, 55253
Offset: 1
Examples
367 is prime, hence 1 is a term. 3666666666667 is prime, hence 11 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((330*10^n+3) div 9)]; // Vincenzo Librandi, Nov 30 2015
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Maple
select(t -> isprime((330*(10^t)+3)/9), [0,seq(seq(6*i+j,j=[1,2,5]),i=0..1000)]); # Robert Israel, Dec 02 2015
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Mathematica
A101840[n_] := If[PrimeQ[((330*(10^n)) + 3)*(1/9)] == True, n, 0]; DeleteDuplicates[Table[A101840[n], {n, 0, 55300}]] (* Abdul Gaffar Khan, Nov 29 2015 *)
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PARI
a=37;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-3)
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PARI
for(n=0,1500,if(isprime((330*10^n+3)/9),print1(n,",")))
Formula
a(n) = A102975(n) - 1.
Extensions
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(12)-a(15) derived from A102975 by Robert Price, Jan 29 2015
Comments