A176083 - OEIS

%I #20 Sep 08 2022 08:45:52

%S 1,4,3,7,24,25,11,7,22,12,9,1,5,69,1,62,41,16,133,89,39,3,162,66,121,

%T 12,4,109,163,85,135,52,251,8,14,6,154,126,167,284,149,158,254,110,

%U 318,23,75,23,59,279,478,513,290,58,256,345,347,25,58,361,672,681,673,697,669,609,278,739,355,529,543,478

%N a(n) = 2^(2n-2) mod prime(2n).

%H G. C. Greubel, <a href="/A176083/b176083.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) = 2^(2n-2) mod A000040(2n).

%e a(20)=89 because (2^(2*20-2) mod prime(2*20))=(274877906944 mod 173)=89.

%p A176083 := proc(n) modp(2^(2*n-2) ,ithprime(2*n)) ; end proc:

%t Table[PowerMod[4, n-1, Prime[2*n]], {n,100}] (* _G. C. Greubel_, Nov 27 2019 *)

%o (Sage) A176083 = lambda n: (2**(2*n-2)) % nth_prime(2*n) # _D. S. McNeil_, Dec 07 2010

%o (PARI) vector(100, n, lift(Mod(4, prime(2*n))^(n-1)) ) \\ _G. C. Greubel_, Nov 27 2019

%o (Magma) [Modexp(4, n-1, NthPrime(2*n)): n in [1..100]]; // _G. C. Greubel_, Nov 27 2019

%Y Cf. A000079, A175803.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Dec 07 2010

%E Corrected and extended by _D. S. McNeil_, Dec 07 2010

%E Terms a(50) onward added by _G. C. Greubel_, Nov 27 2019