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 A070421 a(n) = 7^n mod 38. 1
 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11, 1, 7, 11 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Period 3: repeat [1, 7, 11]. Equivalently 7^n mod 19. - Zerinvary Lajos, Nov 27 2009 LINKS Index entries for linear recurrences with constant coefficients, signature (0,0,1). FORMULA From R. J. Mathar, Apr 20 2010: (Start) a(n) = a(n-3) for n>2. G.f.: ( 1+7*x+11*x^2 ) / ( (1-x)*(1+x+x^2) ). (End) a(n) = (1/9)*(49*(n mod 3)+7*((n+1) mod 3)+((n+2) mod 3)). - Paolo P. Lava, May 14 2010 a(n) = (19 - 16*cos(2*n*Pi/3) - 4*sqrt(3)*sin(2*n*Pi/3))/3. - Wesley Ivan Hurt, Jun 29 2016 MAPLE seq(op([1, 7, 11]), n=0..50); # Wesley Ivan Hurt, Jun 29 2016 MATHEMATICA PowerMod[7, Range[0, 50], 38] (* G. C. Greubel, Mar 21 2016 *) PROG (Sage) [power_mod(7, n, 19) for n in xrange(0, 90)] # or: [power_mod(7, n, 38) for n in xrange(0, 90)] # Zerinvary Lajos, Nov 27 2009 (PARI) a(n)=lift(Mod(7, 19)^n) \\ Charles R Greathouse IV, Mar 22 2016 (MAGMA) [Modexp(7, n, 19): n in [0..100]]; // Bruno Berselli, Mar 22 2016 CROSSREFS Sequence in context: A133346 A091920 A036934 * A213671 A050081 A144076 Adjacent sequences:  A070418 A070419 A070420 * A070422 A070423 A070424 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, May 12 2002 STATUS approved

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