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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A160353 Numbers of the form pqr, where p<q<r are odd primes such that r = +/-1 (mod pq). 3
435, 465, 861, 885, 903, 915, 1335, 1743, 2211, 2235, 2265, 2485, 2667, 2685, 2715, 3081, 3165, 3507, 3585, 3615, 4035, 4065, 4323, 4431, 4865, 4965, 5151, 5253, 5271, 5385, 5835, 5995, 6123, 6153, 6285, 6315, 6441, 6501, 6567, 6735, 7077, 7185, 7385 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Kaplan (2007) has shown that this is a subsequence of A117223 (and thus of A160350; see there for the reference), i.e. the cyclotomic polynomial phi(n) has coefficients in {0,1,-1} for indices n listed here.

This is a subsequence of A160352 which drops the requirement p>2.

See A160350 for further details and references.

LINKS

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

EXAMPLE

a(1)=435=3*5*29 is the smallest product of odd primes p<q<r such that r is congruent to +/- 1 modulo the product of the smaller factors, p*q.

PROG

(PARI) forstep( pqr=1, 9999, 2, my(f=factor(pqr)); #f~==3 & vecmax(f[, 2])==1 & abs((f[3, 1]+1)%(f[1, 1]*f[2, 1])-1)==1 & print1(pqr", "))

CROSSREFS

Sequence in context: A145318 A054987 A054905 * A268475 A212227 A237302

Adjacent sequences:  A160350 A160351 A160352 * A160354 A160355 A160356

KEYWORD

nonn

AUTHOR

M. F. Hasler, May 11 2009

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 17 18:42 EST 2018. Contains 317276 sequences. (Running on oeis4.)