A216469 a(n) = smallest m such that 2n-1 | (2^m+1)/3, or 0 if no such m exists.

1, 3, 0, 0, 9, 5, 0, 0, 0, 9, 0, 0, 0, 27, 0, 0, 15, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 9, 29, 0, 0, 0, 33, 0, 0, 0, 0, 0, 0, 81, 41, 0, 0, 0, 0, 0, 0, 0, 45, 0, 0, 0, 53, 0, 0, 0, 0, 0, 0, 55, 0, 0, 0, 21, 65, 0, 0, 0, 69, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 81, 0, 0

Offset: 1

Author

V. Raman, Sep 07 2012

Keywords

• nonn

Crossrefs

Cf. A003558, A002326, A216829, A216833.

Cf. A216833 (multiplicative order of 2 mod 3*(2n-1)).

Cf. A216829 (value of the half of the multiplicative order of 2 mod 3*(2n-1)).

Programs

Mathematica

Table[s = MultiplicativeOrder[2, 3*(2*n-1), {-1}]; If[IntegerQ[s], s, 0], {n, 100}] (* T. D. Noe, Sep 11 2012 *)

PARI

for(i=0,200,i++;m=0;for(x=0,i,x++;if(((2^x+1)/3)%i==0,m=x;break));print1(m",")) \\ V. Raman, Nov 22 2012