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Rearrangement of natural numbers by choosing alternately even and odd numbers such that every partial sum a(1)+...+a(n) is composite.
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%I #5 Dec 05 2013 19:55:38

%S 4,5,6,1,2,3,12,7,8,9,18,11,10,15,14,13,16,17,24,19,20,21,30,23,22,25,

%T 26,27,28,29,32,31,34,33,38,35,36,37,40,39,42,41,46,43,44,45,50,47,48,

%U 49,54,51,52,53,56,55,58,57,60,59,62,61,66,63,64,65,68,67,70,69,74,71

%N Rearrangement of natural numbers by choosing alternately even and odd numbers such that every partial sum a(1)+...+a(n) is composite.

%e The first number must be composite, so a(1) = 4; next number must be odd and a(2) = 1 or 3 would make a(1)+a(2) prime, so a(2) = 5; etc.

%Y Cf. A075567.

%K nonn,easy

%O 1,1

%A _Amarnath Murthy_, Sep 25 2002

%E Extended by _Ray Chandler_, Feb 13 2005