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A102027 Indices of primes in sequence defined by A(0) = 13, A(n) = 10*A(n-1) + 43 for n > 0. 1

%I

%S 0,1,7,25,43,166,184,3817,8740,50794

%N Indices of primes in sequence defined by A(0) = 13, A(n) = 10*A(n-1) + 43 for n > 0.

%C Numbers n such that (160*10^n - 43)/9 is prime.

%C Numbers n such that digit 1 followed by n >= 0 occurrences of digit 7 followed by digit 3 is prime.

%C Numbers corresponding to terms <= 184 are certified primes.

%C a(11) > 10^5. - _Robert Price_, Feb 11 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/1/17773.htm#prime">Prime numbers of the form 177...773</a>.

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

%F a(n) = A102942(n) - 1.

%e 173 is prime, hence 1 is a term.

%o (PARI) a=13;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+43)

%o (PARI) for(n=0,1500,if(isprime((160*10^n-43)/9),print1(n,",")))

%Y Cf. A000533, A002275, A102942.

%K nonn,hard,more

%O 1,3

%A _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004

%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008

%E a(10) from _Robert Price_, Feb 11 2015

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Last modified June 4 01:52 EDT 2020. Contains 334812 sequences. (Running on oeis4.)