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 A170822 Let p = n-th prime; a(n) = (p-1)/(order of A170821(n) mod p). 1

%I

%S 1,3,2,2,1,1,2,1,1,12,1,1,2,1,2,4,1,14,2,1,2,1,2,1,1,2,2,1,1,10,1,3,1,

%T 1,4,9,2,1,2,18,2,16,1,1,1,1,2,2,1,2,6,2,1,2,1,1,2,1,1,1,3,10,12,1,1,

%U 42,2,12,1,2,1,4,27,2,1,4,1,6,2,6,10,4,3,2,1,2,1,1,2,2,1,2,3,2,1,5

%N Let p = n-th prime; a(n) = (p-1)/(order of A170821(n) mod p).

%H I. Anderson and D. A. Preece, <a href="http://dx.doi.org/10.1016/j.disc.2008.09.046">Combinatorially fruitful properties of 3*2^(-1) and 3*2^(-2) modulo p</a>, Discr. Math., 310 (2010), 312-324.

%e n=3: p=5, A170821(n)=2, order of 2 mod 5 = 4, (5-1)/4 = 1 = a(3).

%o (PARI) f(n) = my(p=prime(n), k=0); while(Mod(4*k, p) != 3, k++); k; \\ A170821

%o a(n) = my(p=prime(n)); (p-1)/znorder(Mod(f(n), p)); \\ _Michel Marcus_, Dec 04 2018

%Y Cf. A001917, A170820, A170821.

%K nonn

%O 3,2

%A _N. J. A. Sloane_, Dec 24 2009

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Last modified May 13 19:36 EDT 2021. Contains 343868 sequences. (Running on oeis4.)