%I M0949 #20 Oct 24 2023 06:19:00
%S 1,2,4,5,6,8,9,11,13,14,15,17,18,20,22,23,24,26,28,29,30,32,34,35,36,
%T 38,40,41,42,43,45,47,48,50,51,53,55,56,57,59,60,61,64
%N a(n) gives position of first n in A057561.
%D R. L. Graham et al., On extremal density theorems for linear forms, pp. 103-109 of H. Zassenhaus, editor, Number Theory and Algebra. Academic Press, NY, 1977.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H Steven R. Finch, <a href="/FinchTriple.html">Triple-Free Sets of Integers</a> [From Steven Finch, Apr 20 2019]
%Y Cf. A057561, A094708.
%K nonn
%O 1,2
%A _N. J. A. Sloane_
%E Edited by _Steven Finch_, Feb 25 2009
%E Revised by _N. J. A. Sloane_, Jun 13 2012
%E a(21) corrected and more terms from _Sean A. Irvine_, Nov 18 2015