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A346567
Fermat pseudoprimes to base 2 that are palindromic in base 2.
1
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
OFFSET
1,1
COMMENTS
There are 133 terms below 2^64. Only 4 of them are also Carmichael numbers (561, 1105, 278545 and 67371265).
LINKS
EXAMPLE
341 is a term since 341 = 101010101_2 is palindromic in base 2, it is composite (= 11 * 31) and 2^340 == 1 (mod 341).
MATHEMATICA
pspQ[n_] := CompositeQ[n] && PowerMod[2, n-1, n] == 1; Select[Range[10^6], PalindromeQ[IntegerDigits[#, 2]] && pspQ[#] &]
CROSSREFS
Intersection of A001567 and A006995.
A065341 and A281576 are subsequences.
Sequence in context: A001567 A178723 A210993 * A328691 A006970 A007011
KEYWORD
nonn,base
AUTHOR
Amiram Eldar, Jul 23 2021
STATUS
approved