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 1-10 of 15 results. Next

A162692 Strictly positive numbers n such that 28*n/(28+n) are integers.

Original entry on oeis.org

21, 28, 70, 84, 168, 364, 756
Offset: 1

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Comments

The 28th row of A127730.
The ansatz 28*n/(28+n)=j (any integer j) yields n=28*j/(28-j) which demonstrates that the sequence is finite if n>=0. [R. J. Mathar, Jul 13 2009]

Crossrefs

Programs

  • Mathematica
    f[a_,b_]:=(a*b)/(a+b); a=28;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]],AppendTo[lst,n]],{n,9!}];lst

Extensions

Edited by R. J. Mathar, Jul 13 2009

A162693 Strictly positive numbers n such that 30*n/(30+n) are integers.

Original entry on oeis.org

6, 15, 20, 30, 45, 60, 70, 120, 150, 195, 270, 420, 870
Offset: 1

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Comments

The 30th row of A127730.
The ansatz 30*n/(30+n)=j (any integer j) yields n=30*j/(30-j) which demonstrates that the sequence is finite if n>=0. [R. J. Mathar, Jul 13 2009]

Crossrefs

Programs

  • Mathematica
    f[a_,b_]:=(a*b)/(a+b); a=30;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]],AppendTo[lst,n]],{n,9!}];lst
    Select[Range[1000],IntegerQ[(30#)/(30+#)]&] (* Harvey P. Dale, Sep 25 2019 *)

Extensions

Edited by R. J. Mathar, Jul 13 2009

A162694 Strictly positive numbers n such that 36*n/(36+n) are integers.

Original entry on oeis.org

12, 18, 36, 45, 72, 108, 126, 180, 288, 396, 612, 1260
Offset: 1

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Comments

The 36th row of A127730.
The ansatz 36*n/(36+n) = j (any integer j) yields n = 36*j/(36-j) which demonstrates that the sequence is finite if n >= 0. - R. J. Mathar, Jul 13 2009
Positive integers n such that half of the harmonic mean of 36 and n is an integer. - Wesley Ivan Hurt, Sep 07 2014

Crossrefs

Programs

  • Mathematica
    Select[Range[1000], IntegerQ[36#/(36 + #)] &] (* Alonso del Arte, Sep 06 2014 *)

Extensions

Edited by R. J. Mathar, Jul 13 2009

A162817 Positive numbers n such that 40*n/(40+n) are integers.

Original entry on oeis.org

10, 24, 40, 60, 120, 160, 280, 360, 760, 1560
Offset: 1

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Keywords

Crossrefs

Programs

  • Mathematica
    f[a_,b_]:=(a*b)/(a+b); a=40;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]], AppendTo[lst,n]],{n,9!}];lst
    Select[Range[1600],IntegerQ[(40#)/(40+#)]&] (* Harvey P. Dale, Oct 11 2011 *)

Extensions

Keywords fini,full added by R. J. Mathar, Jul 31 2009

A162818 Strictly positive numbers n such that (42*n)/(42+n) is an integer.

Original entry on oeis.org

7, 21, 42, 56, 84, 105, 154, 210, 252, 399, 546, 840, 1722
Offset: 1

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Crossrefs

Programs

  • Mathematica
    f[a_,b_]:=(a*b)/(a+b); a=42;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]],AppendTo[lst,n]],{n,9!}];lst
    Select[Range[2000], Divisible[42 #, 42 + #] &] (* Harvey P. Dale, May 09 2012 *)

Extensions

Keywords fini and full added by Franklin T. Adams-Watters, Aug 07 2009

A162819 Positive numbers n such that 48*n/(48+n) are integers.

Original entry on oeis.org

16, 24, 48, 80, 96, 144, 208, 240, 336, 528, 720, 1104, 2256
Offset: 1

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Crossrefs

Programs

  • Mathematica
    f[a_,b_]:=(a*b)/(a+b); a=48;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]], AppendTo[lst,n]],{n,9!}];lst
    Select[Range[2300],IntegerQ[(48#)/(48+#)]&] (* Harvey P. Dale, Dec 18 2018 *)

Extensions

Keywords fini,full added by R. J. Mathar, Jul 31 2009

A162820 Positive numbers n such that 60*n/(60+n) are integers.

Original entry on oeis.org

12, 15, 20, 30, 40, 60, 84, 90, 120, 140, 165, 180, 240, 300, 340, 390, 540, 660, 840, 1140, 1740, 3540
Offset: 1

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Author

Keywords

Crossrefs

Programs

  • Mathematica
    f[a_,b_]:=(a*b)/(a+b); a=60;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]], AppendTo[lst,n]],{n,9!}];lst

Extensions

Keywords fini,full added by R. J. Mathar, Jul 31 2009

A162821 Positive numbers k such that 30*k/(30-k) are integers.

Original entry on oeis.org

5, 10, 12, 15, 18, 20, 21, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 39, 40, 42, 45, 48, 50, 55, 60, 66, 75, 80, 90, 105, 120, 130, 180, 210, 255, 330, 480, 930
Offset: 1

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Comments

The number k=30 is explicitly included, treating the result of division through zero as an integer.
Row 30 of A191973.

Crossrefs

Programs

  • Maple
    for m from 1 to 930 do if(m=30 or m*30 mod (m-30) = 0)then printf("%d, ", m): fi: od: # Nathaniel Johnston, Jun 22 2011
  • Mathematica
    f[a_,b_]:=(a*b)/(a-b); a=30;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]], AppendTo[lst,n]],{n,9!}];lst

Extensions

Keywords fini,full added by R. J. Mathar, Jul 31 2009

A162822 Positive numbers k such that 36*k/(36-k) are integers.

Original entry on oeis.org

9, 12, 18, 20, 24, 27, 28, 30, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 45, 48, 52, 54, 60, 63, 72, 84, 90, 108, 117, 144, 180, 198, 252, 360, 468, 684, 1332
Offset: 1

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Comments

The number k=36 is explicitly included, treating the result of division through zero as an integer.
Row 36 of A191973.

Crossrefs

Programs

  • Maple
    for m from 1 to 1332 do if(m=36 or m*36 mod (m-36) = 0)then printf("%d, ", m): fi: od: # Nathaniel Johnston, Jun 22 2011
  • Mathematica
    f[a_,b_]:=(a*b)/(a-b); a=36;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]], AppendTo[lst,n]],{n,9!}];lst
    Sort[Join[{36},Select[Range[1500],IntegerQ[(36#)/(36-#)]&]]]  (* Harvey P. Dale, Mar 23 2011 *)

Extensions

Keywords fini,full added by R. J. Mathar, Jul 31 2009

A162823 Positive numbers k such that 42*k/(42-k) are integers.

Original entry on oeis.org

6, 14, 21, 24, 28, 30, 33, 35, 36, 38, 39, 40, 41, 42, 43, 44, 45, 46, 48, 49, 51, 54, 56, 60, 63, 70, 78, 84, 91, 105, 126, 140, 168, 189, 238, 294, 336, 483, 630, 924, 1806
Offset: 1

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Author

Keywords

Comments

The number k=42 is explicitly included, treating the result of division through zero as an integer.
Row 42 of A191973.

Crossrefs

Programs

  • Maple
    for m from 1 to 1806 do if(m=42 or m*42 mod (m-42) = 0)then printf("%d, ", m): fi: od: # Nathaniel Johnston, Jun 22 2011
  • Mathematica
    f[a_,b_]:=(a*b)/(a-b); a=42;lst={};Do[If[f[a,n]==IntegerPart[f[a,n]], AppendTo[lst,n]],{n,9!}];lst
    Join[{42},Select[Range[2000],IntegerQ[(42#)/(42-#)]&]]//Quiet//Sort (* Harvey P. Dale, Mar 14 2020 *)

Extensions

Keywords fini,full added by R. J. Mathar, Jul 31 2009
Showing 1-10 of 15 results. Next