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 A101970 Indices of primes in sequence defined by A(0) = 23, A(n) = 10*A(n-1) + 53 for n > 0. 1
 0, 1, 6, 27, 72, 294, 493, 597, 2599, 3729, 7548, 15864 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Numbers n such that (260*10^n - 53)/9 is prime. Numbers n such that digit 2 followed by n >= 0 occurrences of digit 8 followed by digit 3 is prime. Numbers corresponding to terms <= 597 are certified primes. a(13) > 10^5. - Robert Price, Apr 18 2014 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 288...883. FORMULA a(n) = A102961(n+1) - 1. EXAMPLE 283 is prime, hence 1 is a term. MATHEMATICA Select[Range[0, 100000], PrimeQ[(260*10^# - 53)/9] &] (* Robert Price, Apr 18 2015 *) PROG (PARI) a=23; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+53) (PARI) for(n=0, 1500, if(isprime((260*10^n-53)/9), print1(n, ", "))) CROSSREFS Cf. A000533, A002275, A102961. Sequence in context: A273408 A085788 A027276 * A136105 A239568 A198958 Adjacent sequences:  A101967 A101968 A101969 * A101971 A101972 A101973 KEYWORD nonn,hard,more AUTHOR Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 23 2004 EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008 a(12) derived from A102961 by Robert Price, Apr 18 2015 STATUS approved

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Last modified February 21 18:44 EST 2020. Contains 332107 sequences. (Running on oeis4.)