cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-3 of 3 results.

A075249 x-value of the solution (x,y,z) to 5/n = 1/x + 1/y + 1/z satisfying 0 < x < y < z and having the largest z-value. The y and z components are in A075250 and A075251.

Original entry on oeis.org

1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 13, 14, 13, 13, 13, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 18
Offset: 3

Views

Author

T. D. Noe, Sep 10 2002

Keywords

Comments

See A075248 for more details.

Crossrefs

Cf. A075248, A075250, A075251.

Programs

  • Mathematica
    For[xLst={}; yLst={}; zLst={}; n=3, n<=100, n++, cnt=0; xr=n/5; If[IntegerQ[xr], x=xr+1, x=Ceiling[xr]]; While[yr=1/(5/n-1/x); If[IntegerQ[yr], y=yr+1, y=Ceiling[yr]]; cnt==0&&y>x, While[zr=1/(5/n-1/x-1/y); cnt==0&&zr>y, If[IntegerQ[zr], z=zr; cnt++; AppendTo[xLst, x]; AppendTo[yLst, y]; AppendTo[zLst, z]]; y++ ]; x++ ]]; xLst

Formula

Is a(n) = A047252(n-3)-n+4 ? - Ralf Stephan, Feb 24 2004

A075250 y-value of the solution (x,y,z) to 5/n = 1/x + 1/y + 1/z satisfying 0 < x < y < z and having the largest z-value. The x and z components are in A075249 and A075251.

Original entry on oeis.org

2, 5, 3, 4, 5, 9, 19, 7, 9, 13, 20, 43, 13, 17, 23, 37, 77, 21, 27, 37, 58, 121, 31, 40, 55, 85, 175, 43, 56, 75, 116, 239, 57, 73, 99, 153, 313, 73, 93, 127, 194, 397, 91, 116, 157, 241, 491, 111, 141, 191, 292, 595, 133, 169, 229, 349, 709, 157, 95, 269, 410, 833
Offset: 3

Views

Author

T. D. Noe, Sep 10 2002

Keywords

Comments

See A075248 for more details.

Crossrefs

Cf. A075248, A075249, A075251.

Programs

  • Mathematica
    For[xLst={}; yLst={}; zLst={}; n=3, n<=100, n++, cnt=0; xr=n/5; If[IntegerQ[xr], x=xr+1, x=Ceiling[xr]]; While[yr=1/(5/n-1/x); If[IntegerQ[yr], y=yr+1, y=Ceiling[yr]]; cnt==0&&y>x, While[zr=1/(5/n-1/x-1/y); cnt==0&&zr>y, If[IntegerQ[zr], z=zr; cnt++; AppendTo[xLst, x]; AppendTo[yLst, y]; AppendTo[zLst, z]]; y++ ]; x++ ]]; yLst

A075248 Number of solutions (x,y,z) to 5/n = 1/x + 1/y + 1/z satisfying 0 < x < y < z.

Original entry on oeis.org

0, 1, 2, 1, 1, 3, 5, 9, 6, 3, 12, 5, 18, 15, 10, 5, 21, 11, 22, 18, 15, 8, 55, 30, 15, 20, 43, 20, 45, 5, 24, 35, 23, 36, 53, 10, 21, 52, 62, 6, 62, 12, 73, 69, 16, 11, 92, 38, 84, 34, 50, 11, 77, 56, 80, 45, 38, 34, 142, 6, 23, 96, 53, 53, 67, 15, 66, 70, 124, 12, 148, 21, 57
Offset: 2

Views

Author

T. D. Noe, Sep 10 2002

Keywords

Comments

All of the solutions can be printed by removing the comment symbols from the Mathematica program. For the solution (x,y,z) having the largest z value, see (A075249, A075250, A075251). See A073101 for the 4/n conjecture due to Erdős and Straus.

Examples

			a(4)=2 because there are two solutions: 5/4 = 1/1 + 1/5 + 1/20 and 5/4 = 1/1 + 1/6 + 1/12.

Links

Crossrefs

Cf. A073101, A075249, A075250, A075251.

Programs

  • Mathematica
    m = 5; For[lst = {}; n = 2, n <= 100, n++, cnt = 0; xr = n/m; If[IntegerQ[xr], xMin = xr + 1, xMin = Ceiling[xr]]; If[IntegerQ[3xr], xMax = 3xr - 1, xMax = Floor[3xr]]; For[x = xMin, x <= xMax, x++, yr = 1/(m/n - 1/x); If[IntegerQ[yr], yMin = yr + 1, yMin = Ceiling[yr]]; If[IntegerQ[2yr], yMax = 2yr + 1, yMax = Ceiling[2yr]]; For[y = yMin, y <= yMax, y++, zr = 1/(m/n - 1/x - 1/y); If[y > x && zr > y && IntegerQ[zr], z = zr; cnt++; (*Print[n, " ", x, " ", y, " ", z]*)]]]; AppendTo[lst, cnt]]; lst
f[n_] := Length@ Solve[5/n == 1/x + 1/y + 1/z && 0 < x < y < z, {x, y, z}, Integers]; Array[f, 74] (* Robert G. Wilson v, Jul 17 2013 *)
Showing 1-3 of 3 results.

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