%I A080427
%S A080427 1,1,2,4,1,5,10,1,7,14,1,9,19,1,12,24,1,15,30,1,17,34,1,20,40,1,22,44,
               1,
%T A080427 25,50,1,27,54,1,29,59,1,32,64,1,35,70,1,37,74,1,39,79,1,42,84,1,45,90,
%U A080427 1,47,94,1,49,99,1,52,104,1,55,110,1,57,114,1,60,120,1,62,124,1,65,130
%N A080427 a(1)=1 and, for n>1, a(n) is the smallest positive integer such that 
               the absolute difference |a(n)-a(n-1)| has not occurred previously.
%C A080427 It appears (1) that a(3n+2)=1 for n=1,2,3,... and (2) that the sequence 
               {a(3n+3)-a(3n)}={3,2,2,3,3,2,3,2,3,2,2,3,3,2,2,3,3,2,...} consists 
               only of 2's and 3's and that the sequence of the lengths of runs 
               of consecutive 3's in {a(3n+3)-a(3n)} is given by {1,2,1,1,2,2,2,
               1,...}=A026465.
%Y A080427 Cf. A026465.
%Y A080427 Sequence in context: A094640 A070937 A059573 this_sequence A118906 A085059 
               A124037
%Y A080427 Adjacent sequences: A080424 A080425 A080426 this_sequence A080428 A080429 
               A080430
%K A080427 nonn
%O A080427 1,3
%A A080427 John W. Layman (layman(AT)math.vt.edu), Feb 19 2003