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A093162
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Primes of the form 20*R_k + 3, where R_k is the repunit (A002275) of length k.
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3
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OFFSET
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1,1
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COMMENTS
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The next term (a(7)) has 95 digits. - Harvey P. Dale, Dec 26 2022
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LINKS
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Table of n, a(n) for n=1..6.
Makoto Kamada, Prime numbers of the form 22...223.
Index entries for primes involving repunits
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FORMULA
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a(n) = (20*10^A056656(n) + 7)/9 = (2*10^A096506(n) + 7)/9.
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MATHEMATICA
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Select[Table[FromDigits[PadLeft[{3}, n, 2]], {n, 40}], PrimeQ] (* Harvey P. Dale, Dec 26 2022 *)
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CROSSREFS
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Cf. A002275, A056656 (corresponding k, and count of digits 2 in a(n)), A096506.
Sequence in context: A093135 A305754 A202997 * A328808 A206763 A306154
Adjacent sequences: A093159 A093160 A093161 * A093163 A093164 A093165
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KEYWORD
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nonn
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AUTHOR
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Rick L. Shepherd, Mar 26 2004
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EXTENSIONS
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Edited by Ray Chandler, Feb 27 2012
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STATUS
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approved
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