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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified June 20 05:29 EDT 2024. Contains 373512 sequences. (Running on oeis4.)