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 A102007 Indices of primes in sequence defined by A(0) = 17, A(n) = 10*A(n-1) - 63 for n > 0. 1
 0, 1, 3, 7, 8, 23, 59, 109, 133, 221, 411, 699, 998, 1382, 5075, 5542, 6343, 14599, 15092, 21716, 23635, 30220, 50710 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Numbers n such that 10*10^n + 7 is prime. Numbers n such that digit 1 followed by n >= 0 occurrences of digit 0 followed by digit 7 is prime. Numbers corresponding to terms <= 998 are certified primes. a(24) > 2*10^5. - Robert Price, Nov 09 2015 REFERENCES Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. LINKS Makoto Kamada, Prime numbers of the form 100...007. FORMULA a(n) = A088274(n) - 1. EXAMPLE 10007 is prime, hence 3 is a term. MATHEMATICA Select[Range[0, 100000], PrimeQ[10*10^# + 7] &] (* Robert Price, Nov 09 2015 *) PROG (PARI) a=17; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-63) (PARI) for(n=0, 1500, if(isprime(10*10^n+7), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A088274. Sequence in context: A268111 A244532 A037208 * A152486 A301523 A105756 Adjacent sequences:  A102004 A102005 A102006 * A102008 A102009 A102010 KEYWORD nonn,hard,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004 EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 STATUS approved

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Last modified October 23 03:21 EDT 2019. Contains 328335 sequences. (Running on oeis4.)