%I #13 Jan 17 2019 13:44:06
%S 2,8,16,152,193,640,674,1460,26428,48460,72734
%N Indices of primes in sequence defined by A(0) = 87, A(n) = 10*A(n-1) - 53 for n > 0.
%C Numbers n such that (730*10^n + 53)/9 is prime.
%C Numbers n such that digit 8 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime.
%C Numbers corresponding to terms <= 674 are certified primes.
%C a(12) > 10^5. - Robert Price, Oct 09 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/8/81117.htm#prime">Prime numbers of the form 811...117</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A103072(n) - 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
%e 8117 is prime, hence 2 is a term.
%t Select[Range[0, 100000], PrimeQ[(730*10^# + 53)/9] &] (* _Robert Price_, Oct 09 2015 *)
%o (PARI) a=87;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-53)
%o (PARI) for(n=0,1500,if(isprime((730*10^n+53)/9),print1(n,",")))
%Y Cf. A000533, A002275, A103072.
%K nonn,hard,more
%O 1,1
%A _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 30 2004
%E a(9)-a(10) from Kamada data by _Ray Chandler_, Apr 29 2015
%E a(11) from _Robert Price_, Oct 09 2015
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