%I #13 Apr 16 2024 22:22:32
%S 1,2,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,
%T 31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,
%U 54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77
%N 1, 2 and all numbers >= 10.
%C Used to illustrate Besicovitch's density theorem.
%C Equals A171891 + A171892, where + denotes the usual sum of two sequences.
%D H. Halberstam and K. F. Roth, Sequences, Oxford, 1966; see p. 6.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%o (PARI) a(n)=if(n<3,n,n+7) \\ _Charles R Greathouse IV_, Sep 02 2011
%Y Cf. A171891, A171892.
%K nonn,easy,changed
%O 1,2
%A _N. J. A. Sloane_, Oct 19 2010
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