A146746 Numbers n such that sigma_1(n+1)*sigma_1(n)/(sigma_1(n+1)+sigma_1(n))=c, c an integer.

5, 14, 54, 55, 56, 58, 70, 87, 88, 89, 114, 118, 123, 125, 178, 201, 204, 206, 220, 246, 354, 358, 417, 419, 459, 478, 500, 534, 549, 594, 604, 620, 646, 654, 663, 715, 718, 753, 834, 835, 838, 894, 957

Offset

1,1

Comments

A000203(n+1)*A000203(n)/(A000203(n+1)+A000203(n)) = c, c an integer.

Same as A073541. - Georg Fischer, Nov 02 2018

Links

Table of n, a(n) for n=1..43.

Mathematica

sQ[n_]:=Module[{sn=DivisorSigma[1, n], sn1=DivisorSigma[1, n+1]}, Divisible[sn sn1, sn+sn1]]; Select[Range[1000], sQ]  (* Harvey P. Dale, Apr 21 2011 *)

Crossrefs

Cf. A083795, A063647, A073541, A000203.

Sequence in context: A197601 A133751 A005504 * A073541 A268887 A055488

Adjacent sequences: A146743 A146744 A146745 * A146747 A146748 A146749

Keyword

easy,nonn

Author

Ctibor O. Zizka, Nov 01 2008

Extensions

Corrected by Harvey P. Dale, Apr 21 2011

Status

approved