A057764 - OEIS

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A057764

Triangle T(n,k) = number of nonzero elements of multiplicative order k in Galois field GF(2^n) (n >= 1, 1 <= k <= 2^n-1).

1, 1, 0, 2, 1, 0, 0, 0, 0, 0, 6, 1, 0, 2, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 30, 1, 0, 2, 0, 0, 0, 6, 0, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 12, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 36

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OFFSET

1,4

LINKS

Robert Israel, Table of n, a(n) for n = 1..16369 (rows 1 to 13, flattened)

FORMULA

From Robert Israel, Jul 21 2016: (Start)

T(n,k) = A000010(k) if k is a divisor of 2^n-1, otherwise 0.

Sum_{k=1..2^n-1} T(n,k) = 2^n-1 = A000225(n).

G.f. as triangle: g(x,y) = Sum_{j>=0} x^A002326(j)*A000010(2j+1)*y^(2j+1)/(1-x^A002326(j)). (End)

EXAMPLE

Table begins:

1, 0, 2;

1, 0, 0, 0, 0, 0, 6;

...

MAPLE

f:= proc(n, k) if 2^n-1 mod k = 0 then numtheory:-phi(k) else 0 fi end proc:

seq(seq(f(n, k), k=1..2^n-1), n=1..10); # Robert Israel, Jul 21 2016

MATHEMATICA

T[n_, k_] := If[Divisible[2^n - 1, k], EulerPhi[k], 0];

Table[T[n, k], {n, 1, 10}, {k, 1, 2^n - 1}] // Flatten (* Jean-François Alcover, Feb 07 2023, after Robert Israel *)

PROG

(Magma) {* Order(g) : g in GF(2^6) | g ne 0 *};

CROSSREFS

Cf. A000010, A000225, A002326, A053287.

Sequence in context: A277627 A037857 A037875 * A010108 A033782 A302721

Adjacent sequences: A057761 A057762 A057763 * A057765 A057766 A057767

KEYWORD

nonn,easy,nice,tabf

AUTHOR

N. J. A. Sloane, Nov 01 2000

EXTENSIONS

T(6,21) corrected by Robert Israel, Jul 21 2016

STATUS

approved