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A109734
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In A109732, the number 2n+1 appears in position a(n).
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5
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1, 2, 5, 3, 30, 6, 28, 4, 38, 26, 11, 7, 36, 29, 14, 8, 201, 39, 34, 27, 180, 12, 175, 9, 199, 37, 46, 31, 25, 15, 178, 10, 242, 202, 49, 40, 197, 35, 54, 32, 192, 158, 23, 13, 208, 176, 57, 16, 240, 200, 61, 41, 83, 47, 195, 33, 121, 42, 67, 17, 190, 179, 70, 18, 689, 243
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OFFSET
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0,2
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LINKS
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EXAMPLE
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9 appears in position 30 in A109732, so a(4) = 30.
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MAPLE
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with(LinearAlgebra);
hit:=Array(1..200000); a:=[1, 3, 7];
hit[1]:=1; hit[3]:=2; hit[7]:=3; S:={15}; L:=7;
for n from 4 to 20000 do
if (L mod 3 = 0) and hit[L/3]=0 then
L:=L/3; a:=[op(a), L]; hit[L]:=n; S:= S minus {L};
if hit[2*L+1]=0 then S:=S union {2*L+1}; fi;
else L:=min(S); a:=[op(a), L]; hit[L]:=n; S:=S minus {L};
if hit[2*L+1]=0 then S:=S union {2*L+1}; fi;
fi;
od:
#a;
w:=[];
for i from 0 to 50000 do
if hit[2*i+1]=0 then break; fi;
w:=[op(w), hit[2*i+1]]; od:
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MATHEMATICA
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(* using the M generated in A109732 *) ms=Sort[M]; k=1; While[ms[[k]]==2k-1, k++ ]; k=k-1; Take[Ordering[M], k] (* T. D. Noe, Aug 10 2005 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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