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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A001074 Numbers n such that Sum_{k=0..n-1} exp(2*Pi*i*k^3/n) != 0. 1
1, 4, 7, 8, 9, 13, 19, 25, 27, 28, 31, 32, 36, 37, 43, 49, 52, 56, 61, 63, 64, 67, 72, 73, 76, 79, 91, 97, 100, 103, 104, 108, 109, 117, 121, 124, 125, 127, 133, 139, 148, 151, 152, 157, 163, 169, 171, 172, 175, 181, 189, 193, 196, 199, 200, 211, 216, 217 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Mark n points around horizontal disk with labels 0..n-1; place coins at positions k^3 mod n for k=0..n-1; sequence gives n's for which disk does not balance.

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

EXAMPLE

8 is in sequence because 4 coins go at 0, 1 each at 1, 3, 5, 7, so disk is unbalanced in direction of point 0. 12 is not in sequence because there are 2 coins at 0, 4, 8; 1 coin at 1, 3, 5, 7, 9, 11, so disk balanced.

MATHEMATICA

Select[Range[300], Sum[Exp[2 Pi*I*k^3/#], {k, 0, # - 1}] != 0 &] (* T. D. Noe, Jun 25 2012 *)

CROSSREFS

Sequence in context: A289631 A076680 A235623 * A214206 A026316 A283767

Adjacent sequences:  A001071 A001072 A001073 * A001075 A001076 A001077

KEYWORD

nice,nonn,easy

AUTHOR

R. Lozyniak, (11(AT)onna.com)

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 February 19 18:31 EST 2018. Contains 299356 sequences. (Running on oeis4.)