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A080429 Odd numbers such that all a(i)*a(j) with i<j are distinct. 1

%I #11 Dec 22 2014 02:03:34

%S 1,3,5,7,9,11,13,17,19,23,25,29,31,37,41,43,47,49,53,59,61,67,71,73,

%T 79,81,83,89,97,101,103,105,107,109,113,121,127,131,137,139,149,151,

%U 157,163,167,169,173,179,181,191,193,197,199,211,223,227,229,233,239,241

%N Odd numbers such that all a(i)*a(j) with i<j are distinct.

%e 49 belongs to this sequence but 45 does not as 45*1 = 9*5.

%p S := {3}: A := array(1..10^3): for m from 1 to 10^3 do A[m] := 0 od: A[1] := 1: A[3] := 3: for n from 5 to 10^3-1 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 10^3-1 by 2 do if A[i]>0 then printf(`%d,`, A[i]) fi: od: # _James A. Sellers_, Feb 25 2003

%Y Cf. A062090.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Feb 20 2003

%E More terms from _James A. Sellers_, Feb 25 2003

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Last modified April 24 05:44 EDT 2024. Contains 371918 sequences. (Running on oeis4.)