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 (1,-1,1). - R. J. Mathar, Apr 20 2010
FORMULA
From R. J. Mathar, Apr 20 2010: (Start)
a(n) = a(n-1) - a(n-2) + a(n-3).
G.f.: ( -1-6*x-13*x^2 ) / ( (x-1)*(1+x^2) ). (End)
From G. C. Greubel, Mar 20 2016: (Start)
a(n) = a(n-4).
E.g.f.: 10*exp(x) - 9*cos(x) - 3*sin(x). (End)
MATHEMATICA
PowerMod[7, Range[0, 50], 30] (* G. C. Greubel, Mar 20 2016 *)
LinearRecurrence[{1, -1, 1}, {1, 7, 19}, 90] (* or *) PadRight[{}, 90, {1, 7, 19, 13}] (* Harvey P. Dale, Aug 09 2020 *)
PROG
(Sage) [power_mod(7, n, 30) for n in range(0, 84)] # Zerinvary Lajos, Nov 27 2009
(PARI) a(n) = lift(Mod(7, 30)^n); \\ Altug Alkan, Mar 20 2016
(Magma) [Modexp(7, n, 30): n in [0..100]]; // Bruno Berselli, Mar 22 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, May 12 2002
STATUS
approved