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

0,2

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)

Example

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

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 *)

Crossrefs

Cf. A109732. For records see A109739 and A109740.

Sequence in context: A246556 A264137 A308949 * A239309 A077073 A307126

Adjacent sequences: A109731 A109732 A109733 * A109735 A109736 A109737

Keyword

nonn

Author

N. J. A. Sloane, Aug 10 2005

Extensions

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

Status

approved