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

1,2

Links

Table of n, a(n) for n=1..84.

Mathematica

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

Prog

(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

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)).

Sequence in context: A363767 A011073 A200287 * A319359 A104751 A265828

Adjacent sequences: A216466 A216467 A216468 * A216470 A216471 A216472

Keyword

nonn

Author

V. Raman, Sep 07 2012.

Status

approved