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A070406 a(n) = 7^n mod 15. 1
1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1, 7, 4, 13, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (0,0,0,1).

FORMULA

From Paolo P. Lava, Feb 25 2010: (Start)

a(n) = (1/24)*{97*(n mod 4)-29*[(n+1) mod 4]+43*[(n+2) mod 4]-11*[(n+3) mod 4]}, with n>=0.

a(n) = (25/4)-(3/4-3/2*I)*I^n-15/4*(-1)^n-(3/4+3/2*I)*(-I)^n, with n>=0 and I=sqrt(-1). (End)

From R. J. Mathar, Apr 20 2010: (Start)

a(n) = a(n-4).

G.f.: ( -1-7*x-4*x^2-13*x^3 ) / ( (x-1)*(1+x)*(1+x^2) ). (End)

E.g.f.: (1/2)*(5*cosh(x) + 20*sinh(x) - 3*cos(x) - 6*sin(x)). - G. C. Greubel, Mar 20 2016

MATHEMATICA

PowerMod[7, Range[0, 50], 15] (* G. C. Greubel, Mar 20 2016 *)

PROG

(Sage) [power_mod(7, n, 15) for n in xrange(0, 93)] # Zerinvary Lajos, Nov 27 2009

(PARI) a(n) = lift(Mod(7, 15)^n); \\ Altug Alkan, Mar 20 2016

(MAGMA) [Modexp(7, n, 15): n in [0..100]]; // Bruno Berselli, Mar 22 2016

CROSSREFS

Sequence in context: A069199 A138339 A107827 * A279806 A181138 A279942

Adjacent sequences:  A070403 A070404 A070405 * A070407 A070408 A070409

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, May 12 2002

STATUS

approved

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Last modified June 27 15:12 EDT 2017. Contains 288790 sequences.