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A101538
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Indices of primes in sequence defined by A(0) = 63, A(n) = 10*A(n-1) + 53 for n > 0.
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1
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1, 2, 7, 49, 55, 71, 107, 131, 181, 1099, 1367, 1604, 5131, 22681
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OFFSET
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1,2
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COMMENTS
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Numbers n such that (620*10^n - 53)/9 is prime.
Numbers n such that digit 6 followed by n >= 0 occurrences of digit 8 followed by digit 3 is prime.
Numbers corresponding to terms <= 181 are certified primes.
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REFERENCES
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Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
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LINKS
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FORMULA
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EXAMPLE
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683 is prime, hence 1 is a term.
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MATHEMATICA
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Flatten[Position[NestList[10#+53&, 63, 1700], _?(PrimeQ[#]&)]]-1 (* Harvey P. Dale, Sep 24 2013 *)
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PROG
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(PARI) a=63; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+53)
(PARI) for(n=0, 1500, if(isprime((620*10^n-53)/9), print1(n, ", ")))
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 06 2004
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008
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STATUS
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approved
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