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A073797 a(n) = 2^n mod pi(n).

%I A073797 #19 Sep 08 2022 08:45:06
%S A073797 0,0,0,2,1,0,0,0,0,3,1,2,4,2,4,4,1,0,0,0,0,5,1,2,4,8,7,2,4,2,4,8,5,10,
%T A073797 9,8,4,8,4,6,12,2,4,8,2,8,1,2,4,8,1,0,0,0,0,0,0,8,16,2,4,8,16,14,10,3,
%U A073797 6,12,5,8,16,2,4,8,16,11,1,6,12,2,4,18,13,3,6,12,1,8,16,8,16,8,16,8,16
%N A073797 a(n) = 2^n mod pi(n).
%H A073797 Michael De Vlieger, <a href="/A073797/b073797.txt">Table of n, a(n) for n = 2..10000</a>
%F A073797 a(n) = A000079(n) mod A000720(n).
%e A073797 From _Michael De Vlieger_, Dec 09 2018: (Start)
%e A073797 a(2) = 0 since 2^2 mod PrimePi(2) = 4 mod 1 = 0.
%e A073797 a(5) = 2 since 2^5 mod PrimePi(5) = 32 mod 3 = 2. (End)
%t A073797 Array[Mod[2^#, PrimePi@ #] &, 95, 2] (* _Michael De Vlieger_, Dec 09 2018 *)
%t A073797 Table[PowerMod[2,n,PrimePi[n]],{n,2,100}] (* _Harvey P. Dale_, Aug 30 2021 *)
%o A073797 (PARI) for(n=2, 100, print1(lift(Mod(2^n, primepi(n))), ", ")) \\ _G. C. Greubel_, Dec 10 2018
%o A073797 (Magma) [2^n mod #PrimesUpTo(n): n in [2..100]]; // _G. C. Greubel_, Dec 10 2018
%o A073797 (Sage) [mod(2^n, prime_pi(n)) for n in (2..100)] # _G. C. Greubel_, Dec 10 2018
%Y A073797 Cf. A000079, A000720, A015910, A062173, A064367.
%K A073797 nonn
%O A073797 2,4
%A A073797 _Labos Elemer_, Aug 12 2002