A070539 a(n) = n^4 mod 20.

0, 1, 16, 1, 16, 5, 16, 1, 16, 1, 0, 1, 16, 1, 16, 5, 16, 1, 16, 1, 0, 1, 16, 1, 16, 5, 16, 1, 16, 1, 0, 1, 16, 1, 16, 5, 16, 1, 16, 1, 0, 1, 16, 1, 16, 5, 16, 1, 16, 1, 0, 1, 16, 1, 16, 5, 16, 1, 16, 1, 0, 1, 16, 1, 16, 5, 16, 1, 16, 1, 0, 1, 16, 1, 16, 5, 16, 1, 16, 1, 0, 1, 16, 1, 16, 5, 16

Offset

0,3

Comments

Equivalently: n^(4*m + 4) mod 20. - G. C. Greubel, Apr 05 2016

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, 0, 0, 0, 0, 0, 0, 1).

Formula

From G. C. Greubel, Apr 05 2016: (Start)

a(10*n) = 0.

a(n+10) = a(n).

G.f.: (x +16*x^2 +x^3 +16*x^4 +5*x^5 +16*x^6 +x^7 +16*x^8 +x^9)/(1 - x^10). (End)

Mathematica

PowerMod[Range[0, 100], 4, 20] (* G. C. Greubel, Apr 05 2016 *)

Prog

(Sage) [power_mod(n, 4, 20)for n in range(0, 87)] # Zerinvary Lajos, Oct 31 2009
(PARI) a(n)=n^4%20 \\ Charles R Greathouse IV, Apr 05 2016

Crossrefs

Sequence in context: A141682 A040270 A303327 * A301909 A070583 A133821

Adjacent sequences: A070536 A070537 A070538 * A070540 A070541 A070542

Keyword

nonn,easy

Author

N. J. A. Sloane, May 13 2002

Status

approved