%I #19 Jan 17 2019 13:44:06
%S 0,1,2,7,17,19,30,41,102,174,180,530,705,1076,1176,1551,19736,32196,
%T 51507,58274,62232,90032
%N Indices of primes in sequence defined by A(0) = 53, A(n) = 10*A(n-1) - 27 for n > 0.
%C Numbers n such that 50*10^n + 3 is prime.
%C Numbers n such that digit 5 followed by n >= 0 occurrences of digit 0 followed by digit 3 is prime.
%C Numbers corresponding to terms <= 705 are certified primes.
%C a(23) > 2*10^5. - _Robert Price_, Aug 03 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/5/50003.htm#prime">Prime numbers of the form 500...003</a>.
%F a(n) = A096254(n) - 1.
%e 5003 is prime, hence 2 is a term.
%t Select[Range[0, 200000], PrimeQ[50*10^# + 3] &] (* _Robert Price_, Aug 03 2015 *)
%o (PARI) a=53;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-27)
%o (PARI) for(n=0,1500,if(isprime(50*10^n+3),print1(n,",")))
%Y Cf. A000533, A002275, A096254.
%K nonn,more
%O 1,3
%A _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004
%E 1551 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
%E a(17)-a(22) from Kamada data by _Ray Chandler_, Apr 30 2015