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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 Christopher Hunt Gribble, Flattened irregular triangle, for 2 < j < 1000. 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 Cf: A164823, A165252. Sequence in context: A075105 A265675 A094020 * A358462 A141465 A263216 Adjacent sequences: A165606 A165607 A165608 * A165610 A165611 A165612 KEYWORD nonn,tabf AUTHOR Christopher Hunt Gribble, Sep 22 2009 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.)