A200878 Composite numbers whose prime factors have equal numbers of bits.

4, 6, 8, 9, 12, 16, 18, 24, 25, 27, 32, 35, 36, 48, 49, 54, 64, 72, 81, 96, 108, 121, 125, 128, 143, 144, 162, 169, 175, 192, 216, 243, 245, 256, 288, 289, 323, 324, 343, 361, 384, 391, 432, 437, 486, 493, 512, 527, 529, 551, 576, 589, 625, 648, 667, 713

Offset

1,1

Links

Arkadiusz Wesolowski, Table of n, a(n) for n = 1..10000

Example

7429 = 17*19*23 -> 10001*10011*10111, therefore 7429 is a term.
7430 = 2*5*743 -> 10*101*1011100111, therefore 7430 is not a term.

Mathematica

lst = {}; Do[b = IntegerDigits[FactorInteger[n], 2]; If[! PrimeQ[n] && Length[b[[-1, 1]]] == Length[b[[1, 1]]], AppendTo[lst, n]], {n, 4, 6!}]; lst (* Arkadiusz Wesolowski, Dec 03 2011 *)
Select[Range[800], CompositeQ[#]&&Length[Union[IntegerLength[ #, 2]&/@ FactorInteger[ #][[All, 1]]]]==1&] (* Harvey P. Dale, Oct 11 2021 *)

Prog

(PARI) is(n)=my(f=factor(n)[, 1]); #binary(f[1])==#binary(f[#f])&&!isprime(n) \\ Charles R Greathouse IV, Dec 23 2011

Crossrefs

Supersequence of A085721 and of A182302.

Sequence in context: A090419 A209799 A028958 * A344030 A350706 A036310

Adjacent sequences: A200875 A200876 A200877 * A200879 A200880 A200881

Keyword

base,nonn

Author

Arkadiusz Wesolowski, Nov 23 2011

Status

approved