%I
%S 1,2,1,3,4,2,5,3,6,7,4,8,5,9,6,10,11,7,12,8,13,9,14,10,15,16,11,17,12,
%T 18,13,19,14,20,15,21,22,16,23,17,24,18,25,19,26,20,27,21,28,29,22,30,
%U 23,31,24,32,25,33,26,34,27,35,28,36,37,29,38,30,39,31,40,32,41,33,42
%N Positive integers, each occurring twice in the sequence, such that a(n) = a(k) when n+k = 4*a(n), starting with a(1)=1 and filling the next vacant position with the smallest unused number.
%C Positions where n occurs are A001614(n) and 4*nA001614(n), where A001614 is the Connell sequence: 1 odd, 2 even, 3 odd, ...
%F a(4*a(n)n) = a(n). Limit a(n)/n = 1/2. Limit (a(n+1)a(n))/sqrt(n) = 1.
%F a( A001614(n) ) = n; a( 4n  A001614(n) ) = n.
%e 9 first appears at position: A001614(9) = 14;
%e 9 next appears at position: 4*9  A001614(9) = 22.
%o (PARI) {a(n)=local(A=vector(n),m=1); for(k=1,n,if(A[k]==0,A[k]=m;if(4*mk<=#A,A[4*mk]=m);m+=1));A[n]}
%Y Cf. A117385 (a(5*a(n)n)=a(n)), A117386 (a(6*a(n)n)=a(n)).
%Y Cf. A001614 (Connell sequence).
%K nonn
%O 1,2
%A _Paul D. Hanna_, Mar 11 2006
