login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A099477 Numbers having no divisors d such that also d+2 is a divisor. 4
1, 2, 5, 7, 10, 11, 13, 14, 17, 19, 22, 23, 25, 26, 29, 31, 34, 37, 38, 41, 43, 46, 47, 49, 50, 53, 55, 58, 59, 61, 62, 65, 67, 71, 73, 74, 77, 79, 82, 83, 85, 86, 89, 91, 94, 95, 97, 98, 101, 103, 106, 107, 109, 110, 113, 115, 118, 119, 121, 122, 125, 127, 130, 131, 133 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A099475(a(n)) = 0: complement of A059267.

Except for 3, all primes are in this sequence. - Alonso del Arte, Jun 13 2014

LINKS

Table of n, a(n) for n=1..65.

EXAMPLE

10 is in the sequence because its divisors are 1, 2, 5, 10, none of which is 2 less than another.

11 is in the sequence as are all primes other than 3.

12 is not in the sequence because its divisors are 1, 2, 3, 4, 6, 12, of which 2 and 4 are 2 less than another divisor.

MATHEMATICA

twinDivsQ[n_] := Union[ IntegerQ[ # ] & /@ (n/(Divisors[n] + 2))][[ -1]] == True; Select[ Range[133], !twinDivsQ[ # ] &] (* Robert G. Wilson v, Jun 09 2005 *)

d2noQ[n_]:=Module[{d=Divisors[n]}, Intersection[d, d+2]=={}]; Select[ Range[ 150], d2noQ] (* Harvey P. Dale, Feb 15 2019 *)

CROSSREFS

Cf. A108118.

Sequence in context: A142879 A284167 A108118 * A261034 A259749 A067934

Adjacent sequences:  A099474 A099475 A099476 * A099478 A099479 A099480

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 18 2004

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 19 04:40 EDT 2019. Contains 328211 sequences. (Running on oeis4.)