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Rearrangement of natural numbers by choosing alternately odd and even numbers such that every partial sum is composite.
1

%I #11 Jun 17 2017 03:04:36

%S 9,6,1,2,3,4,5,8,7,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,

%T 27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,

%U 50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72

%N Rearrangement of natural numbers by choosing alternately odd and even numbers such that every partial sum is composite.

%C a(n) = n for n > 9.

%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>9,n,[9, 6, 1, 2, 3, 4, 5, 8, 7][n]) \\ _Charles R Greathouse IV_, Sep 02 2011

%Y Cf. A075566.

%K nonn,easy

%O 1,1

%A _Amarnath Murthy_, Sep 25 2002

%E Extended by _Ray Chandler_, Feb 13 2005