A109734 In A109732, the number 2n+1 appears in position a(n).

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

Offset: 0

Author

N. J. A. Sloane, Aug 10 2005

Keywords

• nonn

Examples

			9 appears in position 30 in A109732, so a(4) = 30.
		

Links

• N. J. A. Sloane and Alois P. Heinz, Table of n, a(n) for n = 0..20000 (first 1024 terms from N. J. A. Sloane)

Crossrefs

Cf. A109732. For records see A109739 and A109740.

Programs

Maple

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:
w; # N. J. A. Sloane, Aug 25 2015

Mathematica

(* 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 *)

Extensions

More terms from T. D. Noe and Ray Chandler, Aug 10 2005