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%I #21 Jan 17 2019 13:44:06
%S 0,1,7,8,14,19,25,37,44,64,111,243,302,392,559,838,1008,1018,1172,
%T 1333,2235,2628,4425,8847,20811,37743,72925,86286
%N Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n-1) - 9 for n > 0.
%C Numbers n such that 60*10^n + 1 is prime.
%C Numbers n such that digit 6 followed by n >= 0 occurrences of digit 0 followed by digit 1 is prime.
%C Numbers corresponding to terms <= 838 are certified primes.
%C Certified primality of numbers corresponding to terms 1008,1018,1172,1333 with Primo. - _Ryan Propper_, Jun 20 2005
%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/6/60001.htm#prime">Prime numbers of the form 600...001</a>.
%F a(n) = A056805(n+1) - 1.
%e 600000001 is prime, hence 7 is a term.
%o (PARI) a=61;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-9)
%o (PARI) for(n=0,1500,if(isprime(60*10^n+1),print1(n,",")))
%Y Cf. A000533, A002275, A056805.
%K nonn,hard,more
%O 1,3
%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) and _Stefan Steinerberger_, Apr 28 2007
%E More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
%E a(26)-a(28) from Kamada data by _Ray Chandler_, Apr 23 2015
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