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 A101517 Indices of primes in sequence defined by A(0) = 61, A(n) = 10*A(n-1) - 9 for n > 0. 1
 0, 1, 7, 8, 14, 19, 25, 37, 44, 64, 111, 243, 302, 392, 559, 838, 1008, 1018, 1172, 1333, 2235, 2628, 4425, 8847, 20811, 37743, 72925, 86286 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Numbers n such that 60*10^n + 1 is prime. Numbers n such that digit 6 followed by n >= 0 occurrences of digit 0 followed by digit 1 is prime. Numbers corresponding to terms <= 838 are certified primes. Certified primality of numbers corresponding to terms 1008,1018,1172,1333 with Primo. - Ryan Propper, Jun 20 2005 REFERENCES Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467. LINKS Table of n, a(n) for n=1..28. Makoto Kamada, Prime numbers of the form 600...001. FORMULA a(n) = A056805(n+1) - 1. EXAMPLE 600000001 is prime, hence 7 is a term. PROG (PARI) a=61; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-9) (PARI) for(n=0, 1500, if(isprime(60*10^n+1), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A056805. Sequence in context: A037368 A281710 A037970 * A271953 A165465 A047521 Adjacent sequences: A101514 A101515 A101516 * A101518 A101519 A101520 KEYWORD nonn,hard,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004 EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm) and Stefan Steinerberger, Apr 28 2007 More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008 a(26)-a(28) from Kamada data by Ray Chandler, Apr 23 2015 STATUS approved

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Last modified April 15 13:47 EDT 2024. Contains 371689 sequences. (Running on oeis4.)