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

Author

Arkadiusz Wesolowski, Nov 23 2011

Keywords

• base
• nonn

Examples

			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.
		

Links

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

Crossrefs

Supersequence of A085721 and of A182302.

Programs

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 *)

PARI

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