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A072823 Numbers that are not the sum of two powers of 2. 5

%I #32 Mar 08 2019 07:22:38

%S 1,7,11,13,14,15,19,21,22,23,25,26,27,28,29,30,31,35,37,38,39,41,42,

%T 43,44,45,46,47,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,67,69,70,

%U 71,73,74,75,76,77,78,79,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,97

%N Numbers that are not the sum of two powers of 2.

%C 1 and integers with three or more 1-bits in their binary expansion. - _Vladimir Baltic_, Jul 23 2002

%C A073267(a(n)) = 0. [_Reinhard Zumkeller_, Mar 07 2012]

%C Appears to be the numbers k >1 for which there exist an x and y (x>y) such that x OR y = k, x+y != k, and x<k. - _Gary Detlefs_, Jun 02 2014

%H Reinhard Zumkeller, <a href="/A072823/b072823.txt">Table of n, a(n) for n = 1..10000</a>

%p f:= x -> convert(convert(x,base,2),`+`)>2:

%p {1} union select(f, {$2..1000}); # _Robert Israel_, Jun 08 2014

%t Join[{1}, Select[Range[100], DigitCount[#, 2, 1] >= 3&]] (* _Jean-François Alcover_, Mar 08 2019 *)

%o (Haskell)

%o a072823 n = a072823_list !! (n-1)

%o a072823_list = tail $ elemIndices 0 a073267_list

%o -- _Reinhard Zumkeller_, Mar 07 2012

%Y Cf. A048645, A000027.

%K nonn

%O 1,2

%A _Jeremy Gardiner_, Jul 21 2002

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Last modified March 29 04:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)