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A192521
Monotonic ordering of set S generated by these rules: if x and y are in S then floor((x+1)(y+1)/2) is in S, and 2 is in S.
2
2, 4, 7, 12, 19, 20, 30, 31, 32, 46, 48, 49, 50, 52, 70, 73, 75, 76, 77, 79, 80, 82, 84, 106, 111, 114, 115, 117, 120, 121, 122, 124, 125, 127, 128, 130, 132, 136, 160, 168, 172, 174, 177, 181, 183, 184, 185, 187, 188, 189, 190, 192, 193, 195, 196, 199, 200
OFFSET
1,1
MATHEMATICA
start = {2}; f[x_, y_] := Floor[(x + 1)*(y + 1)/2]
b[x_] :=
Block[{w = x},
Select[Union[
Flatten[AppendTo[w,
Table[f[w[[i]], w[[j]]], {i, 1, Length[w]}, {j, 1, i}]]]], # <
400 &]];
t = NestList[b, start, 14][[-1]] (* A192521 *)
Table[t[[i]] - t[[i - 1]], {i, 2, Length[t]}] (* differences *)
CROSSREFS
Cf. A192476.
Sequence in context: A230118 A105807 A209616 * A066699 A188425 A087149
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jul 03 2011
STATUS
approved