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 A155751 A variation on 10^n mod 17 2
 1, -7, -2, -3, 4, 6, -8, 5, -1, 7, 2, 3, -4, -6, 8, -5, 1, -7, -2, -3, 4, 6, -8, 5, -1, 7, 2, 3, -4, -6, 8, -5, 1, -7, -2, -3, 4, 6, -8, 5, -1, 7, 2, 3, -4, -6, 8, -5, 1, -7, -2, -3, 4, 6, -8, 5, -1, 7, 2, 3, -4, -6, 8, -5, 1, -7, -2, -3, 4, 6, -8, 5, -1, 7, 2, 3, -4, -6, 8, -5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS This is 10^n mod 17, using values -8,-7,...,7,8 (instead of 0..16). - Don Reble, Sep 02 2017. This sequence can be employed in a test for divisibility by 17 and works like A033940 works for 7. The use of negative coefficients ensures the termination of the test because the modulus of the intermediate sum at each step of the test decreases strictly. The test is successful if the final sum is 0. The negative coefficients have the form (10^n mod 17) - 17 when 10^n mod 17 > 8. Example: 9996 is divisible by 17 since |6*1 + 9*(-7) + 9*(-2) + 9*(-3)| = 102 and 2*1 + 0*(-7) + 1*(-2) = 0. LINKS FORMULA a(n)= -a(n-8). G.f.:(1-7x-2x^2-3x^3+4x^4+6x^5-8x^6+5x^7)/(1+x^8). [From R. J. Mathar, Feb 13 2009] CROSSREFS Cf. A033940, A119910, A117378. Sequence in context: A222224 A163333 A116369 * A092234 A160101 A210975 Adjacent sequences:  A155748 A155749 A155750 * A155752 A155753 A155754 KEYWORD easy,sign AUTHOR Ferruccio Guidi (fguidi(AT)cs.unibo.it), Jan 26 2009, Feb 08 2009 STATUS approved

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Last modified December 11 15:03 EST 2018. Contains 318049 sequences. (Running on oeis4.)