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A101839
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Indices of primes in sequence defined by A(0) = 31, A(n) = 10*A(n-1) + 51 for n > 0.
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1
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0, 5, 10, 12, 18, 22, 66, 107, 117, 175, 672, 779, 1087, 1218, 1655, 6244, 10738, 12589, 17512, 25999, 32543, 53273
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OFFSET
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1,2
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COMMENTS
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Numbers n such that (330*10^n - 51)/9 is prime.
Numbers n such that digit 3 followed by n >= 0 occurrences of digit 6 followed by digit 1 is prime.
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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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3666661 is prime, hence 5 is a term.
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PROG
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(PARI) a=31; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a+51)
(PARI) for(n=0, 1500, if(isprime((330*10^n-51)/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 20 2004
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EXTENSIONS
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More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
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STATUS
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approved
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