A192650 First differences of A192649.

1, 1, 1, 1, 2, 1, 1, 3, 3, 1, 1, 4, 3, 7, 1, 1, 6, 1, 5, 3, 7, 1, 4, 3, 1, 1, 7, 5, 2, 1, 1, 14, 16, 1, 7, 8, 1, 1, 6, 5, 3, 1, 1, 7, 7, 2, 14, 1, 9, 7, 8, 7, 1, 1, 7, 5, 2, 1, 1, 6, 9, 7, 5, 3, 1, 1, 7, 9, 6, 1, 5, 2, 1, 1, 8, 15, 8, 31, 9, 9, 8, 8, 7, 23, 1, 1, 8, 7, 5, 3, 7, 1, 1, 15, 7, 24, 1

Offset: 1

Author

Clark Kimberling, Jul 06 2011

Keywords

• nonn

Comments

Are there infinitely many pairs 1,1?

Crossrefs

Cf. A192649, A192646.

Programs

Mathematica

start = {1, 2, 4};
f[x_, y_] := If[MemberQ[Range[1, 700], x^2 - y^2], x^2 - 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}]]]], # <
      700 &]];
t = FixedPoint[b, start]  (* A192649 *)
Differences[t] (* A192650 *)