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A331893
Positive numbers k such that both k and -k are a palindromes in negabinary representation.
2
1, 5, 7, 17, 21, 31, 57, 65, 85, 127, 155, 217, 257, 273, 325, 341, 455, 511, 635, 857, 889, 993, 1025, 1105, 1253, 1285, 1365, 1799, 2047, 2159, 2555, 2667, 3417, 3577, 3641, 3937, 4097, 4161, 4369, 4433, 4965, 5125, 5189, 5397, 5461, 6951, 7175, 7967, 8191
OFFSET
1,2
COMMENTS
Numbers of the form 2^(2*m-1) - 1 (A083420) and 2^(2*m) + 1 (A052539) are terms.
LINKS
EXAMPLE
5 is a term since the negabinary representation of 5, 101, and the negabinary representation of -5, 1111, are both palindromic.
MATHEMATICA
negabin[n_] := negabin[n] = If[n==0, 0, negabin[Quotient[n-1, -2]]*10 + Mod[n, 2]]; nbPalinQ[n_] := And @@ (PalindromeQ @ negabin[#] & /@ {n, -n}); Select[Range[2^13], nbPalinQ]
CROSSREFS
Intersection of A331891 and A331892.
Sequence in context: A146949 A048700 A331892 * A331895 A164120 A342799
KEYWORD
nonn,base
AUTHOR
Amiram Eldar, Jan 30 2020
STATUS
approved