%I #15 Jan 17 2019 13:44:06
%S 1,4,5,10,14,68,89,133,188,244,266,269,469,1574,2294,2506,3511,3824,
%T 6856,11021,11656,17498,35035,41965,50557,93061
%N Indices of primes in sequence defined by A(0) = 63, A(n) = 10*A(n-1) + 13 for n > 0.
%C Numbers n such that (580*10^n - 13)/9 is prime.
%C Numbers n such that digit 6 followed by n >= 0 occurrences of digit 4 followed by digit 3 is prime.
%C Numbers corresponding to terms <= 469 are certified primes.
%C a(27) > 10^5. - _Robert Price_, Sep 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/6/64443.htm#prime">Prime numbers of the form 644...443</a>.
%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.
%F a(n) = A103035(n+1) - 1.
%e 6444443 is prime, hence 5 is a term.
%t Select[Range[0, 100000], PrimeQ[(580*10^# - 13)/9] &] (* _Robert Price_, Sep 12 2015 *)
%o (PARI) a=63;for(n=0,1000,if(isprime(a),print1(n,","));a=10*a+13)
%o (PARI) for(n=0,1000,if(isprime((580*10^n-13)/9),print1(n,",")))
%Y Cf. A000533, A002275, A103035.
%K nonn,hard,more
%O 1,2
%A _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004
%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
%E a(20)-a(24) from Kamada data by _Ray Chandler_, Apr 30 2015
%E a(25)-a(26) from _Robert Price_, Sep 12 2015
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