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A346567
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Fermat pseudoprimes to base 2 that are palindromic in base 2.
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1
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341, 561, 645, 1105, 2047, 4369, 4681, 5461, 8481, 16705, 33153, 266305, 278545, 526593, 1052929, 1082401, 1398101, 2113665, 2162721, 2290641, 4259905, 6242685, 7674967, 8388607, 16843009, 17895697, 22369621, 34603041, 67371265, 268505089, 280885153, 285212689
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OFFSET
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1,1
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COMMENTS
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There are 133 terms below 2^64. Only 4 of them are also Carmichael numbers (561, 1105, 278545 and 67371265).
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LINKS
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EXAMPLE
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341 is a term since 341 = 101010101_2 is palindromic in base 2, it is composite (= 11 * 31) and 2^340 == 1 (mod 341).
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MATHEMATICA
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pspQ[n_] := CompositeQ[n] && PowerMod[2, n-1, n] == 1; Select[Range[10^6], PalindromeQ[IntegerDigits[#, 2]] && pspQ[#] &]
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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