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a(n) = n^5 mod 16.
1

%I #14 Apr 16 2023 10:41:12

%S 0,1,0,3,0,5,0,7,0,9,0,11,0,13,0,15,0,1,0,3,0,5,0,7,0,9,0,11,0,13,0,

%T 15,0,1,0,3,0,5,0,7,0,9,0,11,0,13,0,15,0,1,0,3,0,5,0,7,0,9,0,11,0,13,

%U 0,15,0,1,0,3,0,5,0,7,0,9,0,11,0,13,0,15,0,1,0,3,0,5,0,7,0

%N a(n) = n^5 mod 16.

%H Harvey P. Dale, <a href="/A167465/b167465.txt">Table of n, a(n) for n = 0..1000</a>

%F a(n) = a(n-16). G.f. -x*(1+3*x^2+5*x^4+7*x^6+9*x^8+11*x^10+13*x^12+15*x^14) / ( (x-1)*(1+x)*(1+x^2)*(1+x^4)*(1+x^8) ). - _R. J. Mathar_, Jun 28 2011

%t PowerMod[Range[0,90],5,16] (* _Harvey P. Dale_, Sep 26 2012 *)

%o (Sage) [power_mod(n,5,16)for n in range(0, 89)] #

%o (PARI) a(n)=n^5%16 \\ _Charles R Greathouse IV_, Apr 06 2016

%K nonn,easy

%O 0,4

%A _Zerinvary Lajos_, Nov 04 2009