VOOZH about

URL: https://oeis.org/A165609

⇱ A165609 - OEIS

login
A165609
Irregular triangle read by rows: Nonexistent values of cos(2*Pi/k) mod j, for j >= 2 and 1 <= k <= j-1.
2
2, 3, 2, 5, 3, 8, 3, 8, 9, 2, 5, 10, 3, 4, 15, 16, 4, 10, 13, 19, 4, 19, 22, 27, 2, 5, 10, 11, 20, 21, 26, 29, 3, 6, 9, 15, 20, 24, 25, 32, 33, 5, 6, 10, 11, 33, 37, 3, 8, 9, 13, 20, 23, 30, 34, 35, 40, 4, 10, 18, 19, 28, 29, 37, 43
OFFSET
1,1
COMMENTS
See A164823 for explanatory comment and the definition of "cos(x) mod j".
LINKS
EXAMPLE
The irregular triangle of numbers without empty rows is:
j Nonexistent values of cos(2*Pi/k) mod j
4 2
5 3
7 2 5
11 3 8
13 3 8 9
17 2 5 10
19 3 4 15 16
23 4 10 13 19
29 4 19 22 27
31 2 5 10 11 20 21 26 29
37 3 6 9 15 20 24 25 32 33
41 5 6 10 11 33 37
43 3 8 9 13 20 23 30 34 35 40
47 4 10 18 19 28 29 37 43
CROSSREFS
Sequence in context: A075105 A265675 A094020 * A358462 A141465 A263216
KEYWORD
nonn,tabf
AUTHOR
EXTENSIONS
Minor edits from N. J. A. Sloane, Sep 25 2009
Minor edit by Christopher Hunt Gribble, Oct 01 2009
STATUS
approved