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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
OFFSET
0,2
COMMENTS
Period 3: repeat [1, 7, 11].
Equivalently 7^n mod 19. - Zerinvary Lajos, Nov 27 2009
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) = (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 range(0, 90)] # or:
[power_mod(7, n, 38) for n in range(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
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 12 2002
STATUS
approved