A331830 Numbers k such that k and k + 1 are both negabinary evil numbers.

7, 13, 19, 27, 31, 39, 45, 51, 55, 61, 67, 75, 79, 87, 93, 99, 107, 111, 117, 123, 127, 135, 141, 147, 155, 159, 167, 173, 179, 183, 189, 195, 203, 207, 213, 219, 223, 231, 237, 243, 247, 253, 259, 267, 271, 279, 285, 291, 299, 303, 309, 315, 319, 327, 333, 339

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

7 is a term since both 7 and 7 + 1 = 8 are negabinary evil numbers (A268272): 7 has 4 digits of 1 in its negabinary representation, 11011, 8 has 2 digits of 1 in its negabinary representation, 11000, and both 4 and 2 are even.

Mathematica

negaBinWt[n_] := negaBinWt[n] = If[n==0, 0, negaBinWt[Quotient[n-1, -2]] + Mod[n, 2]]; evilNegaBinQ[n_] := EvenQ[negaBinWt[n]]; c = 0; k = 1; s = {}; v = Table[-1, {2}]; While[c < 60, If[evilNegaBinQ[k], v = Join[Rest[v], {k}]; If[AllTrue[Differences[v], # == 1 &], c++; AppendTo[s, k - 1]]]; k++]; s

Crossrefs

Cf. A157970, A268272, A331831.

Sequence in context: A246294 A039281 A045115 * A221027 A211431 A299928

Adjacent sequences: A331827 A331828 A331829 * A331831 A331832 A331833

Keyword

nonn,base

Author

Amiram Eldar, Jan 28 2020

Status

approved