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Search: id:A103405
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| A103405 |
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The 2^n-th palindromic prime. |
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+0
1
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| 2, 3, 7, 151, 757, 14341, 36563, 1114111, 1793971, 7256527, 115737511, 188646881, 746676647, 11984748911, 19541414591, 75174747157, 1192238322911, 1901840481091, 7382419142837, 115344262443511, 181836161638181
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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2, 3, 5, 7, 11, 101, 131, 151, 181, 191, 313, 353, 373, 383, 727 and 757 are the first sixteen palindromic primes.
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MATHEMATICA
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NextPalindrome[n_] := Block[ {lg = Floor@ Log[10, n] + 1, idn = IntegerDigits@ n}, If[ Union@ idn == {9}, Return[n + 2], If[lg < 2, Return[n + 1], If[ FromDigits@ Reverse@ Take[ idn, Ceiling[lg/2]] > FromDigits@ Take[ idn, -Ceiling[lg/2]], FromDigits@ Join[ Take[ idn, Ceiling[lg/2]], Reverse@ Take[ idn, Floor[lg/2]]], idfhn = FromDigits@ Take[ idn, Ceiling[lg/2]] + 1; idp = FromDigits@ Join[ IntegerDigits@ idfhn, Drop[ Reverse@ IntegerDigits@ idfhn, Mod[lg, 2]]] ]]]];
c = 0; pal = 0; Do[ While[c < 2^n, pal = NextPalindrome@ pal; If[ PrimeQ@ pal, c++ ]]; Print@ pal, {n, 0, 20}]
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CROSSREFS
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Cf. A083816.
Adjacent sequences: A103402 A103403 A103404 this_sequence A103406 A103407 A103408
Sequence in context: A083436 A088856 A007013 this_sequence A087311 A053924 A130060
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KEYWORD
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base,nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 04 2005, corrected Nov 16 2006
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