

A139799


Integers k with at least one divisor d > 1 that divides (n/d)+1.


1



2, 6, 10, 12, 14, 15, 18, 20, 22, 24, 26, 28, 30, 33, 34, 38, 42, 44, 45, 46, 50, 51, 54, 56, 58, 60, 62, 66, 69, 70, 72, 74, 76, 78, 82, 86, 87, 90, 91, 92, 94, 95, 96, 98, 102, 105, 106, 108, 110, 114, 118, 120, 122, 123, 124, 126, 130, 132, 134, 138, 140
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OFFSET

1,1


COMMENTS

Previous name: Sequence of integers n>=2 such that there is an integer k>1 with k divides n and k divides (n/k)+1.
The first square in the sequence is 1225.
First squares are 1225, 8100, 25600, 46225.  Zak Seidov, Nov 14 2012


LINKS

Zak Seidov, Table of n, a(n) for n = 1..10000
J. Malenfant, On the MatrixElement Expansion of a Circulant Determinant, arXiv preprint arXiv:1502.06012 [math.NT], 2015.


EXAMPLE

2 is a term since 2 divides 2 and 2/2 + 1.
6 is a term since 3 divides 6 and 6/3 + 1.


MATHEMATICA

okQ[n_] := Sum[Divisible[n/d+1, d] // Boole, {d, Divisors[n] // Rest}] > 0;
Select[Range[140], okQ] (* JeanFrançois Alcover, Aug 10 2018 *)


PROG

(PARI) isok(n) = sumdiv(n, d, (d>1) && !(((n/d)+1) % d)) >= 1; \\ Michel Marcus, May 08 2018


CROSSREFS

Sequence in context: A133520 A099017 A298748 * A214586 A305634 A139710
Adjacent sequences: A139796 A139797 A139798 * A139800 A139801 A139802


KEYWORD

nonn


AUTHOR

Juan Lopez Gonzalez (e44625(AT)estudiante.uam.es), Jun 14 2008


EXTENSIONS

Number 37 corrected to 38 by Zak Seidov, Nov 14 2012
New name from Michel Marcus, May 08 2018


STATUS

approved



