A168354 Squarefree semiprimes whose binary expansion is palindromic.

15, 21, 33, 51, 65, 85, 93, 119, 129, 219, 341, 365, 381, 403, 427, 471, 511, 633, 717, 771, 843, 951, 1057, 1137, 1241, 1273, 1285, 1317, 1397, 1501, 1651, 1707, 1799, 1967, 2047, 2049, 2661, 2973, 3579, 3687, 3831, 4097, 4321, 4369, 4529, 4593, 4681

Offset

1,1

Links

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

Example

15 = 3*5 = {1,1,1,1}.
21 = 3*7 = {1,0,1,0,1}.
33 = 3*11 = {1,0,0,0,0,1}.

Mathematica

f1[n_]:=Reverse[IntegerDigits[n, 2]]==IntegerDigits[n, 2]; f2[n_]:=Last/@FactorInteger[n]=={1, 1}; lst={}; Do[If[f1[n]&&f2[n], AppendTo[lst, n]], {n, 8!}]; lst

Crossrefs

Cf. A016041.

Intersection of A006995 and A006881. - Michel Marcus, Nov 24 2020

Sequence in context: A043326 A179996 A079814 * A190358 A090999 A123912

Adjacent sequences: A168351 A168352 A168353 * A168355 A168356 A168357

Keyword

nonn,base

Author

Vladimir Joseph Stephan Orlovsky, Nov 23 2009

Status

approved