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A101129
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Indices of primes in sequence defined by A(0) = 73, A(n) = 10*A(n-1) - 27 for n > 0.
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1
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0, 3, 5, 15, 21, 38, 102, 162, 239, 1047, 1973, 2558, 5879, 14435, 28337, 32795, 38078, 56778, 91214, 111324, 115862, 138603
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OFFSET
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1,2
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COMMENTS
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Numbers n such that 70*10^n + 3 is prime.
Numbers n such that digit 7 followed by n >= 0 occurrences of digit 0 followed by digit 3 is prime.
Numbers corresponding to terms <= 239 are certified primes.
Certified primality of number corresponding to term 1047 with Primo. - Ryan Propper, Jun 20 2005
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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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7000003 is prime, hence 5 is a term.
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MATHEMATICA
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Select[Range[0, 200000], PrimeQ[70*10^# + 3] &] (* Robert Price, Aug 15 2015 *)
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PROG
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(PARI) a=73; for(n=0, 1500, if(isprime(a), print1(n, ", ")); a=10*a-27)
(PARI) for(n=0, 1500, if(isprime(70*10^n+3), 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 03 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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