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A275285
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Numbers k such that 33*10^k + 7 is prime.
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0
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1, 2, 5, 6, 30, 58, 66, 127, 138, 179, 287, 520, 767, 954, 966, 1254, 1313, 1976, 2266, 2496, 3137, 4058, 4411, 7009, 11736, 12155, 21328, 31124, 31589, 38581, 42683, 54634, 56634, 85297
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OFFSET
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1,2
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COMMENTS
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For k > 0, numbers k such that the digits 33 followed by k-1 occurrences of the digit 0 followed by the digit 7 is prime (see Example section).
a(35) > 10^5.
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LINKS
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EXAMPLE
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5 is in this sequence because 33*10^5 + 7 = 3300007 is prime.
Initial terms and associated primes:
a(1) = 1, 337;
a(2) = 2, 3307;
a(3) = 5, 3300007;
a(4) = 6, 33000007;
a(5) = 30, 33000000000000000000000000000007, etc.
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MATHEMATICA
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Select[Range[0, 100000], PrimeQ[33*10^# + 7] &]
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PROG
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(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(33*10^n+7), print1(n, ", "))); \\ Altug Alkan, Jul 21 2016
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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