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 A080430 a(n) = least odd number such that all pairwise sums a(i) + a(j), i < j <= n, are distinct. 3

%I

%S 1,3,5,9,15,25,41,59,77,105,147,189,255,303,363,423,515,631,747,825,

%T 951,1061,1091,1215,1433,1595,1723,1929,2119,2321,2613,2771,2869,3111,

%U 3443,3667,3867,4115,4521,4993,5397,5747,6121,6393,6663,7257,7423,7735,8279

%N a(n) = least odd number such that all pairwise sums a(i) + a(j), i < j <= n, are distinct.

%H Zak Seidov, <a href="/A080430/b080430.txt">Table of n, a(n) for n = 1..127</a>

%p S := {4}: A := array(1..10^4): for m from 1 to 10^4 do A[m] := 0 od: A[1] := 1: A[3] := 3: for n from 5 to 10^4-1 by 2 do mytest := 0: for j from 1 to n-2 by 2 do if A[j]>0 then if member(A[j]+n, S) then mytest := 1; break; fi:fi:od: if mytest=0 then A[n] := n; for j from 1 to n-2 by 2 do S := S union {A[j]+n} od: fi: od: for i from 1 to 10^4-1 by 2 do if A[i]>0 then printf(`%d,`, A[i]) fi: od: # _James A. Sellers_, Feb 26 2003

%t s = {1, 3}; s2 = {4}; k = 5; Do[Label[kk]; If[Intersection[s + k, s2] == {}, s2 = Flatten[{s + k, s2}]; AppendTo[s, k]]; k = k + 2; If[k < 10000, Goto[kk]], {1}]; s (* _Zak Seidov_, Dec 23 2014 *)

%Y Cf. A080429.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Feb 20 2003

%E More terms from _James A. Sellers_, Feb 26 2003

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Last modified September 29 20:22 EDT 2020. Contains 337432 sequences. (Running on oeis4.)