A070423 a(n) = 7^n mod 40.

1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1, 7, 9, 23, 1

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). - R. J. Mathar, Apr 20 2010

Formula

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

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

G.f.: ( -1 - 7*x - 9*x^2 - 23*x^3 ) / ( (x-1)*(1+x)*(1+x^2) ). (End)

E.g.f.: 5*cosh(x) + 15*sinh(x) - 4*cos(x) - 8*sin(x). - G. C. Greubel, Mar 22 2016

Mathematica

PowerMod[7, Range[0, 100], 40] (* or *) PadRight[{}, 100, {1, 7, 9, 23}] (* Harvey P. Dale, Nov 14 2013 *)

Prog

(Sage) [power_mod(7, n, 40) for n in range(0, 93)] # Zerinvary Lajos, Nov 27 2009
(PARI) a(n)=lift(Mod(7, 40)^n) \\ Charles R Greathouse IV, Mar 22 2016
(Magma) [Modexp(7, n, 40): n in [0..100]]; // Bruno Berselli, Mar 22 2016

Crossrefs

Sequence in context: A032394 A242988 A063486 * A018882 A257332 A350540

Adjacent sequences: A070420 A070421 A070422 * A070424 A070425 A070426

Keyword

nonn,easy

Author

N. J. A. Sloane, May 12 2002

Status

approved