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 A101573 Indices of primes in sequence defined by A(0) = 51, A(n) = 10*A(n-1) + 11 for n > 0. 1
 1, 8, 11, 14, 25, 44, 61, 79, 127, 325, 493, 613, 709, 1640, 1645, 2102, 8513, 8687 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Numbers n such that (470*10^n - 11)/9 is prime. Numbers n such that digit 5 followed by n >= 0 occurrences of digit 2 followed by digit 1 is prime. Numbers corresponding to terms <= 709 are certified primes. a(19) > 10^5. - Robert Price, Jul 04 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 522...221. FORMULA a(n) = A103008(n) - 1. EXAMPLE 521 is prime, hence 1 is a term. PROG (PARI) a=51; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+11) (PARI) for(n=0, 1500, if(isprime((470*10^n-11)/9), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A103008. Sequence in context: A287552 A275191 A279776 * A029629 A028394 A188199 Adjacent sequences:  A101570 A101571 A101572 * A101574 A101575 A101576 KEYWORD nonn,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 09 2004 EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008 STATUS approved

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Last modified March 31 03:48 EDT 2020. Contains 333136 sequences. (Running on oeis4.)