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A101734 Indices of primes in sequence defined by A(0) = 41, A(n) = 10*A(n-1) + 71 for n > 0. 1

%I

%S 0,462

%N Indices of primes in sequence defined by A(0) = 41, A(n) = 10*A(n-1) + 71 for n > 0.

%C Numbers n such that (440*10^n - 71)/9 is prime.

%C Numbers n such that digit 4 followed by n >= 0 occurrences of digit 8 followed by digit 1 is prime.

%C Number corresponding to term 462 is a certified prime. No further terms up to 5000.

%C a(3) > 2*10^5. - _Robert Price_, Oct 15 2015

%D Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/4/48881.htm#prime">Prime numbers of the form 488...881</a>.

%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.

%F a(n) = A102997(n) - 1.

%e 41 is prime, hence 0 is a term.

%o (PARI) a=41;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+71)

%o (PARI) for(n=0,1500,if(isprime((440*10^n-71)/9),print1(n,",")))

%Y Cf. A000533, A002275, A102997.

%K nonn,bref,hard,more

%O 1,2

%A _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 14 2004

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Last modified August 20 06:02 EDT 2019. Contains 326139 sequences. (Running on oeis4.)