OFFSET
0,2
COMMENTS
In binary expansion, 1-bits occur only in groups of two or more, separated from other such groups by at least two 0-bits.
Integers that satisfy A048727(n) = 3*n.
LINKS
MATHEMATICA
filterQ[n_] := !MatchQ[IntegerDigits[n, 2], {1}|{1, 0, ___}|{___, 0, 1}|{___, 1, 0, 1, ___}|{___, 0, 1, 0, ___}];
Select[Range[0, 400], filterQ] (* Jean-François Alcover, Dec 31 2020 *)
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Antti Karttunen, Mar 30 1999
STATUS
approved