cp's OEIS Frontend

A257981 Sequence (a(n)) generated by Rule 3 (in Comments) with a(1) = 1 and d(1) = 1.

%I A257981 #4 Jun 05 2015 03:42:26
%S A257981 1,3,2,5,10,4,8,6,12,7,14,11,22,9,18,36,13,26,15,30,16,32,17,34,24,20,
%T A257981 40,19,38,21,42,23,46,28,56,25,50,41,29,58,31,62,27,54,47,39,78,33,66,
%U A257981 37,74,35,70,44,88,45,90,43,86,48,96,52,104,49,98,57
%N A257981 Sequence (a(n)) generated by Rule 3 (in Comments) with a(1) = 1 and d(1) = 1.
%C A257981 Rule 3 follows.  For k >= 1, let  A(k) = {a(1), …, a(k)} and D(k) = {d(1), …, d(k)}.  Begin with k = 1 and nonnegative integers a(1) and d(1).
%C A257981 Step 1:   If there is an integer h such that 1 - a(k) < h < 0 and h is not in D(k) and a(k) + h is not in A(k), let d(k+1) be the least such h, let a(k+1) = a(k) + h, replace k by k + 1, and repeat Step 1; otherwise do Step 2.
%C A257981 Step 2:  Let h be the least positive integer not in D(k) such that a(k) - h is not in A(k).  Let a(k+1) = a(k) + h and d(k+1) = h.  Replace k by k+1 and do Step 1.
%C A257981 See A257905 for a guide to related sequences and conjectures.
%H A257981 Clark Kimberling, <a href="/A257981/b257981.txt">Table of n, a(n) for n = 1..1000</a>
%e A257981 a(1) = 1, d(1) = 1;
%e A257981 a(2) = 3, d(2) = 2;
%e A257981 a(3) = 2, d(3) = -1;
%e A257981 a(4) = 5, d(4) = 3.
%t A257981 {a, f} = {{1}, {1}}; Do[tmp = {#, # - Last[a]} &[Min[Complement[#, Intersection[a, #]]&[Last[a] + Complement[#, Intersection[f, #]] &[Range[2 - Last[a], -1]]]]];
%t A257981 If[! IntegerQ[tmp[[1]]], tmp = {Last[a] + #, #} &[NestWhile[# + 1 &, 1, ! (! MemberQ[f, #] && ! MemberQ[a, Last[a] - #]) &]]]; AppendTo[a, tmp[[1]]]; AppendTo[f, tmp[[2]]], {120}]; {a, f} (* _Peter J. C. Moses_, May 14 2015 *)
%Y A257981 Cf. A257905, A257982.
%K A257981 nonn,easy
%O A257981 1,2
%A A257981 _Clark Kimberling_, May 19 2015