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A070410
a(n) = 7^n mod 25.
1
1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18, 1, 7, 24, 18
OFFSET
0,2
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-18*x^2 ) / ( (x-1)*(1+x^2) ). (End)
a(n) = 25 - a(n-2), n>=2. - Vincenzo Librandi, Feb 08 2011
From G. C. Greubel, Mar 20 2016: (Start)
a(n) = a(n-4).
E.g.f.: (1/2)*(25*exp(x) - 23*cos(x) - 11*sin(x)). (End)
MATHEMATICA
PowerMod[7, Range[0, 50], 25] (* G. C. Greubel, Mar 20 2016 *)
LinearRecurrence[{1, -1, 1}, {1, 7, 24}, 90] (* or *) PadRight[{}, 90, {1, 7, 24, 18}] (* Harvey P. Dale, Jan 07 2024 *)
PROG
(Sage) [power_mod(7, n, 25) for n in range(0, 84)] # Zerinvary Lajos, Nov 27 2009
(PARI) a(n) = lift(Mod(7, 25)^n); \\ Altug Alkan, Mar 20 2016
(Magma) [Modexp(7, n, 25): n in [0..100]]; // Bruno Berselli, Mar 22 2016
CROSSREFS
Sequence in context: A196113 A286506 A286406 * A377011 A077035 A076602
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, May 12 2002
STATUS
approved