%I A129131
%S A129131 4,2,6,3,8,5,9,7,10,11,12,13,14,17,15,19,16,23,18,29,20,31,21,37,22,41,
%T A129131 24,43,25,47,26,53,27,59,28,61,30,67,32,71,33,73,34,79,35,83,36,89,38,
%U A129131 97,39,101,40,103,42,107,44,109,45,113,46,127,48,131,49,137,50,139,51
%N A129131 Alternately write down composite and prime numbers.
%C A129131 a(2n-1) = A073846(2n+1), a(2n) = A073846(2n).
%e A129131 Lowest composite number is 4, lowest prime number is 2, next composite 
               number after 4 is 6, next prime number after 2 is 3 and so on.
%o A129131 (MAGMA) P:=[ n : n in [2..150] | IsPrime(n) ]; C:=[ n : n in [2..70] 
               | not IsPrime(n) ]; &cat[ [C[k], P[k] ]: k in [1..Minimum(#C, #P)] 
               ]; /* Klaus Brockhaus, Mar 31 2007 */
%Y A129131 Cf. A000040 (prime numbers), A002808 (composite numbers), A018252 (nonprime 
               numbers), A073846 (alternate nonprime and prime numbers).
%Y A129131 Sequence in context: A143308 A163238 A097362 this_sequence A097467 A092205 
               A059853
%Y A129131 Adjacent sequences: A129128 A129129 A129130 this_sequence A129132 A129133 
               A129134
%K A129131 nonn
%O A129131 1,1
%A A129131 Edwin F. Sampang (efs_files(AT)yahoo.com), Mar 30 2007
%E A129131 Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), 
               Mar 31 2007