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A084960
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Initial prime of a prime chain of length n under the iteration x->5x+4.
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8
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2, 3, 5, 83, 263, 5333, 5333, 6714497, 42360737, 3757699889, 3757699889, 1431898413161, 5654774136689
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OFFSET
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1,1
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COMMENTS
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This is a special case of prime chains generated by f(x) = cx + d.
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LINKS
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EXAMPLE
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a(3) = 5 since 5, f(5) = 29 and f(29) = 149 are primes when f(x) = 5x+4.
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MATHEMATICA
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t[p_] := Block[{c=1, q = 5*p+4}, While[ PrimeQ@q, q = 5*q + 4; c++]; c]; a[n_] := Block[{p = 2}, While[t[p] < n, p = NextPrime@ p]; p]; Array[a, 8] (* Giovanni Resta, Mar 21 2017 *)
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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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EXTENSIONS
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STATUS
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approved
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