%I #15 Jan 17 2019 13:44:07
%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