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A084958
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Initial prime of a prime chain of length n under the iteration x->5x+2.
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7
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2, 3, 13, 19, 373, 135859, 135859, 18235423, 26588257, 93112729, 376038903103, 7087694466289, 120223669028389
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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)=13 since 13, f(13)=67 and f(67)=337 are primes when f(x) = 5x+2.
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MATHEMATICA
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c[p_] := Block[{k = 1, q = 5*p+2}, While[ PrimeQ[q], q = 5*q+2; k++]; k]; a[n_] := Block[{p = 2}, While[c[p] < n, p = NextPrime@ p]; p]; Array[a, 7] (* Giovanni Resta, Mar 21 2017 *)
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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