A112983 - OEIS

%I #15 Jan 12 2023 01:38:19

%S 0,0,1,0,4,2,4,0,7,8,4,8,4,8,1,0,4,2,4,12,16,8,4,8,14,8,25,4,4,8,4,0,

%T 16,8,1,20,4,8,16,32,4,2,4,32,34,8,4,32,11,48,16,32,4,2,31,8,16,8,4,

%U 32,4,8,16,0,64,62,4,32,16,18,4,56,4,8,61,32,36,50,4

%N a(n) = 2^(n+1) mod n.

%H T. D. Noe, <a href="/A112983/b112983.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A106262(2*n-1, n-2). - _G. C. Greubel_, Jan 11 2023

%e a(3) = 2^4 mod 3 = 16 mod 3 = 1.

%t Table[PowerMod[2, n + 1, n], {n, 100}] (* _T. D. Noe_, Aug 13 2012 *)

%o (Python)

%o print([2**(n+1) % n for n in range(1,77)])

%o # _Alex Ratushnyak_, Aug 12 2012

%o (Magma) [Modexp(2,n+1,n): n in [1..120]]; // _G. C. Greubel_, Jan 11 2023

%o (SageMath) [power_mod(2,n+1,n) for n in range(1,120)] # _G. C. Greubel_, Jan 11 2023

%Y Cf. A106262, A212844.

%K easy,nonn

%O 1,5

%A _Paul Barry_, Oct 08 2005

%E Name, data and offset corrected by _Alex Ratushnyak_, Aug 12 2012