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 A101571 Indices of primes in sequence defined by A(0) = 57, A(n) = 10*A(n-1) - 53 for n > 0. 1
 22, 52, 12808, 15070 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers n such that (460*10^n + 53)/9 is prime. Numbers n such that digit 5 followed by n >= 0 occurrences of digit 1 followed by digit 7 is prime. Numbers corresponding to terms <= 52 are certified primes. No further terms up to 2400. a(5) > 10^5. - Robert Price, Jun 20 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 511...117. FORMULA a(n) = A103006(n+1) - 1. EXAMPLE 511111111111111111111117 is prime, hence 22 is a term. PROG (PARI) a=57; for(n=0, 1000, if(isprime(a), print1(n, ", ")); a=10*a-53) (PARI) for(n=0, 1000, if(isprime((460*10^n+53)/9), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A103006. Sequence in context: A111576 A277979 A177726 * A290381 A324486 A122502 Adjacent sequences:  A101568 A101569 A101570 * A101572 A101573 A101574 KEYWORD nonn,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004 EXTENSIONS a(3)-a(4) from Kamada data by Ray Chandler, Apr 30 2015 STATUS approved

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Last modified January 17 17:33 EST 2021. Contains 340247 sequences. (Running on oeis4.)