cp's OEIS Frontend

A102007 Indices of primes in sequence defined by A(0) = 17, A(n) = 10*A(n-1) - 63 for n > 0.

%I A102007 #17 Nov 28 2021 03:03:18
%S A102007 0,1,3,7,8,23,59,109,133,221,411,699,998,1382,5075,5542,6343,14599,
%T A102007 15092,21716,23635,30220,50710,221627,350070,371695,487290,995255
%N A102007 Indices of primes in sequence defined by A(0) = 17, A(n) = 10*A(n-1) - 63 for n > 0.
%C A102007 Numbers n such that 10*10^n + 7 is prime.
%C A102007 Numbers n such that digit 1 followed by n >= 0 occurrences of digit 0 followed by digit 7 is prime.
%C A102007 Numbers corresponding to terms <= 998 are certified primes.
%C A102007 a(24) > 2*10^5. - _Robert Price_, Nov 09 2015
%D A102007 Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
%H A102007 Makoto Kamada, <a href="https://stdkmd.net/nrr/1/10007.htm#prime">Prime numbers of the form 100...007</a>.
%F A102007 a(n) = A088274(n) - 1.
%e A102007 10007 is prime, hence 3 is a term.
%t A102007 Select[Range[0, 100000], PrimeQ[10*10^# + 7] &] (* _Robert Price_, Nov 09 2015 *)
%o A102007 (PARI) a=17;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a-63)
%o A102007 (PARI) for(n=0,1500,if(isprime(10*10^n+7),print1(n,",")))
%Y A102007 Cf. A000533, A002275, A088274.
%K A102007 nonn,hard,more
%O A102007 1,3
%A A102007 _Klaus Brockhaus_ and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004
%E A102007 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
%E A102007 a(24)-a(28) added from A088274 by _Amiram Eldar_, Nov 28 2021