login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Squarefree odious numbers.
1

%I #17 Mar 15 2024 02:25:43

%S 1,2,7,11,13,14,19,21,22,26,31,35,37,38,41,42,47,55,59,61,62,67,69,70,

%T 73,74,79,82,87,91,93,94,97,103,107,109,110,115,118,122,127,131,133,

%U 134,137,138,143,145,146,151,155,157,158,161,167,173,174,179,181,182,185,186,191,193,194,199

%N Squarefree odious numbers.

%C Odious numbers that are squarefree numbers.

%H Amiram Eldar, <a href="/A230048/b230048.txt">Table of n, a(n) for n = 1..10000</a>

%t odiousQ[n_] := OddQ @ DigitCount[n, 2][[1]]; Select[Range[200], odiousQ[#] && SquareFreeQ[#] &] (* _Amiram Eldar_, Dec 10 2019 *)

%o (PARI) is(n)=hammingweight(n)%2 && issquarefree(n) \\ _Charles R Greathouse IV_, Mar 18 2014

%Y Intersection of A000069 and A005117.

%K nonn,base

%O 1,2

%A _Irina Gerasimova_, Oct 06 2013

%E Corrected by _R. J. Mathar_, Oct 06 2013