A192520 Monotonic ordering of set S generated by these rules: if x and y are in S then floor(x*y/2) is in S, and 5 is in S.

5, 12, 30, 72, 75, 180, 187, 432, 450, 467, 1080, 1122, 1125, 1167, 2592, 2700, 2802, 2805, 2812, 2917, 6480, 6732, 6750, 7002, 7005, 7012, 7030, 7292, 15552, 16200, 16812, 16830, 16872, 16875, 17484, 17502, 17505, 17512, 17530, 17575, 18230

Offset: 1

Author

Clark Kimberling, Jul 03 2011

Keywords

• nonn

Crossrefs

Cf. A192476.

Programs

Mathematica

start = {5}; f[x_, y_] := Floor[x*y/2]
b[x_] :=
  Block[{w = x},
   Select[Union[
     Flatten[AppendTo[w,
       Table[f[w[[i]], w[[j]]], {i, 1, Length[w]}, {j, 1, i}]]]], # <
      70000 &]];
t = NestList[b, start, 14][[-1]] (* A192520 *)
Table[t[[i]] - t[[i - 1]], {i, 2, Length[t]}]  (* difference sequence *)