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

21, 28, 70, 84, 168, 364, 756

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Jul 10 2009

Keywords

• nonn
• fini
• full

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

Cf. A162688, A162689, A162690, A162691

Cf. A127730. [From Franklin T. Adams-Watters, Aug 07 2009]

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