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%I #16 Jan 17 2019 13:44:06
%S 5,14,35,44,446,1030,1238,3491,6068,13646,17237,56270,72710,75380
%N Indices of primes in sequence defined by A(0) = 93, A(n) = 10*A(n-1) + 43 for n > 0.
%C Numbers n such that (880*10^n - 43)/9 is prime.
%C Numbers n such that digit 9 followed by n >= 0 occurrences of digit 7 followed by digit 3 is prime.
%C Numbers corresponding to terms <= 1030 are certified primes.
%C a(15) > 10^5. - _Robert Price_, Nov 12 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/9/97773.htm#prime">Prime numbers of the form 977...773</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A103106(n+1) - 1.
%e 9777773 is prime, hence 5 is a term.
%t Select[Range[0, 100000], PrimeQ[(880*10^# - 43)/9] &] (* _Robert Price_, Nov 12 2015 *)
%o (PARI) a=93;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+43)
%o (PARI) for(n=0,1500,if(isprime((880*10^n-43)/9),print1(n,",")))
%Y Cf. A000533, A002275, A103106.
%K nonn,hard,more
%O 1,1
%A _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004
%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
%E a(10)-a(11) from Kamada data by _Ray Chandler_, Apr 29 2015
%E a(12)-a(14) from _Robert Price_, Nov 12 2015