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%I #20 Jan 17 2019 13:44:06
%S 0,2,3,14,152,321,470,560,663,2156,3696,14874,19269,22094
%N Indices of primes in sequence defined by A(0) = 97, A(n) = 10*A(n-1) - 43 for n > 0.
%C Numbers n such that (830*10^n + 43)/9 is prime.
%C Numbers n such that digit 9 followed by n >= 0 occurrences of digit 2 followed by digit 7 is prime.
%C Numbers corresponding to terms <= 663 are certified primes.
%C a(15) > 10^5. - Robert Price, Nov 02 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/9/92227.htm#prime">Prime numbers of the form 922...227</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A103095(n) - 1.
%e 92227 is prime, hence 3 is a term.
%t Select[Range[0, 100000], PrimeQ[(830*10^# + 43)/9] &] (* _Robert Price_, Nov 02 2015 *)
%o (PARI) a=97;for(n=0,1000,if(isprime(a),print1(n,","));a=10*a-43)
%o (PARI) for(n=0,1000,if(isprime((830*10^n+43)/9 ),print1(n,",")))
%Y Cf. A000533, A002275, A103095.
%K nonn,hard,more,less
%O 1,2
%A _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Nov 27 2004
%E Two more terms, corresponding to probable primes, from _Ryan Propper_, Jun 21 2005
%E Edited by _T. D. Noe_, Oct 30 2008
%E a(12)-a(14) from Kamada data by _Ray Chandler_, Apr 28 2015
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