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%I #11 Jan 06 2024 19:40:30
%S 1,6,5,2,0,7,4,3,8,8,3,4,7,0,2,5,6,1,1,6,5,2,0,7,4,3,8,8,3,4,7,0,2,5,
%T 6,1,1,6,5,2,0,7,4,3,8,8,3,4,7,0,2,5,6,1,1,6,5,2,0,7,4,3,8,8,3,4,7,0,
%U 2,5,6,1,1,6,5,2,0,7,4,3,8,8,3,4,7,0,2,5,6,1,1,6,5,2,0,7,4,3,8,8,3,4,7,0,2
%N a(n) = (-1)^n*(2*n+1) (mod 9).
%F Period 18 sequence: [1, 6, 5, 2, 0, 7, 4, 3, 8, 8, 3, 4, 7, 0, 2, 5, 6, 1].
%p seq(`mod`((-1)^n*(2*n+1), 9), n = 0..120); # _G. C. Greubel_, Nov 05 2019
%t Table[Mod[(-1)^n*(2*n+1), 9], {n, 0, 120}] (* _G. C. Greubel_, Nov 05 2019 *)
%t Mod[Times@@@Partition[Riffle[Range[1,221,2],{1,-1},{1,-1,2}],2],9] (* _Harvey P. Dale_, Jan 06 2024 *)
%o (PARI) a(n)=((-1)^n*(2*n+1))%9
%o (Magma) [(-1)^n*(2*n+1) mod 9 : n in [0..120]]; // _G. C. Greubel_, Nov 05 2019
%o (Sage) [mod((-1)^n*(2*n+1), 9) for n in (0..120)] # _G. C. Greubel_, Nov 05 2019
%o (GAP) List([0..120], n-> (-1)^n*(2*n+1) mod 9 ); # _G. C. Greubel_, Nov 05 2019
%Y Cf. A112280.
%K nonn
%O 0,2
%A _Paul D. Hanna_, Sep 01 2005
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