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URL: https://oeis.org/A266973

⇱ A266973 - OEIS

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A266973
a(n) = 4^n mod 17.
1
1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16, 13, 1, 4, 16
OFFSET
0,2
COMMENTS
Period 4: repeat [1, 4, 16, 13].
FORMULA
G.f.: (1+4*x+16*x^2+13*x^3)/(1-x^4).
a(n) = a(n-4) for n>3.
From Wesley Ivan Hurt, Jun 29 2016: (Start)
a(n) = (34 - 3*(5 + 3*I)*I^(-n) - 3*(5 - 3*I)*I^n)/4 where I=sqrt(-1).
a(n) = (17 - 15*cos(n*Pi/2) - 9*sin(n*Pi/2))/2. (End)
E.g.f.: (17*exp(x) - 15*cos(x) - 9*sin(x))/2. - Stefano Spezia, Sep 26 2025
MAPLE
A266973:=n->power(4, n) mod 17: seq(A266973(n), n=0..100); # Wesley Ivan Hurt, Jun 29 2016
MATHEMATICA
PowerMod[4, Range[0, 100], 17]
PROG
(Magma) [Modexp(4, n, 17): n in [0..100]];
CROSSREFS
Cf. similar sequences of the type 4^n mod p, where p is a prime: A010685 (5), A153727 (7), A168429 (11), A168430 (13), this sequence (17), A187532 (19).
Sequence in context: A224123 A273579 A147560 * A029659 A265218 A331055
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Apr 06 2016
STATUS
approved