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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

Table of n, a(n) for n=0..89.

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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Last modified March 28 02:00 EDT 2017. Contains 284182 sequences.