A331894 Positive numbers such that both their binary and negabinary representations are palindromic.

0, 1, 3, 5, 7, 17, 21, 31, 51, 65, 85, 127, 195, 257, 273, 325, 341, 455, 511, 771, 819, 1025, 1105, 1285, 1365, 1799, 2047, 3075, 4097, 4161, 4369, 4433, 5125, 5189, 5397, 5461, 7175, 7967, 8191, 12291, 12483, 13107, 16385, 16705, 17425, 17745, 20485, 20805

Offset

1,3

Comments

Numbers of the form 2^(2*m-1) - 1 (A083420) and 2^(2*m) + 1 (A052539) are terms.

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Example

7 is a term since the binary representation of 7, 111, and the negabinary representation of 7, 11011, are both palindromic.

Mathematica

negabin[n_] := negabin[n] = If[n==0, 0, negabin[Quotient[n-1, -2]]*10 + Mod[n, 2]]; Select[Range[0, 2*10^4], And @@ (PalindromeQ /@ {IntegerDigits[#, 2], negabin[#]}) &]

Crossrefs

Intersection of A006995 and A331891.

Cf. A039724, A095309.

Sequence in context: A122853 A137258 A053341 * A357234 A086086 A141772

Adjacent sequences: A331891 A331892 A331893 * A331895 A331896 A331897

Keyword

nonn,base

Author

Amiram Eldar, Jan 30 2020

Status

approved