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A077783
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Numbers k such that (10^k-1)/9 + 4*10^floor(k/2) is a palindromic wing prime (a.k.a. near-repdigit palindromic prime).
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3
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3, 15, 91, 231, 1363, 2497, 4963, 5379, 12397, 26395, 120253, 200145
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OFFSET
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1,1
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COMMENTS
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Prime versus probable prime status and proofs are given in the author's table.
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REFERENCES
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C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
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LINKS
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FORMULA
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EXAMPLE
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15 is a term because (10^15 - 1)/9 + 4*10^7 = 111111151111111.
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MATHEMATICA
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Do[ If[ PrimeQ[(10^n + 36*10^Floor[n/2] - 1)/9], Print[n]], {n, 3, 26400, 2}] (* Robert G. Wilson v, Dec 16 2005 *)
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PROG
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(Magma) [n: n in [3..2000 by 2] | IsPrime((10^n+36*10^(n div 2)-1) div 9)]; // Vincenzo Librandi, Oct 13 2015
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CROSSREFS
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KEYWORD
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more,nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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