login
Numbers that are not the sum of 3 or fewer terms of A277238.
0

%I #15 Feb 18 2021 00:35:31

%S 27,37,47,73,83,87,125,139,141,167,175,197,237,267,273,277,281,305,

%T 307,327,335,337,345,351,379,387,397,405,421,433,463,471,477,487,505,

%U 531,537,547,567,577,589,613,619,629,631,635,659,661,665,687,691,697,703,715,727,731,743,753,789,805,821,857,877,883,919,941

%N Numbers that are not the sum of 3 or fewer terms of A277238.

%C Not known to be infinite. Also, it is not known if every integer is the sum of 4 or fewer terms of A277238, although this is true up to 2^20.

%t Take[#, 66] &@ Complement[Range@ Max@ #, #] &@ Union@ Map[Total, Rest@ Tuples[{0}~Join~#, 3]] &@ Prepend[Select[Range[10^3], If[OddQ@ Length@ # && Take[#, {Ceiling[Length[#]/2]}] == {0}, False, Union[Take[#, Floor[Length[#]/2]] + Reverse@ Take[#, -Floor[Length[#]/2]]] == {1}] &@ IntegerDigits[#, 2] &], 1] (* _Michael De Vlieger_, Nov 25 2016 *)

%Y Cf. A277238.

%K nonn

%O 1,1

%A _Jeffrey Shallit_, Nov 24 2016