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A000020 Number of primitive polynomials of degree n over GF(2). 10
2, 1, 2, 2, 6, 6, 18, 16, 48, 60, 176, 144, 630, 756, 1800, 2048, 7710, 7776, 27594, 24000, 84672, 120032, 356960, 276480, 1296000, 1719900, 4202496, 4741632, 18407808, 17820000, 69273666, 67108864, 211016256, 336849900, 929275200, 725594112, 3697909056 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The initial 2 should really be a 1. See A011260 for official version.

REFERENCES

E. R. Berlekamp, Algebraic Coding Theory, McGraw-Hill, NY, 1968, p. 84.

T. L. Booth, An analytical representation of signals in sequential networks, pp. 301-3240 of Proceedings of the Symposium on Mathematical Theory of Automata. New York, N.Y., 1962. Microwave Research Institute Symposia Series, Vol. XII; Polytechnic Press of Polytechnic Inst. of Brooklyn, Brooklyn, N.Y. 1963 xix+640 pp. See p. 303.

W. W. Peterson and E. J. Weldon, Jr., Error-Correcting Codes. MIT Press, Cambridge, MA, 2nd edition, 1972, p. 476.

M. P. Ristenblatt, Pseudo-Random Binary Coded Waveforms, pp. 274-314 of R. S. Berkowitz, editor, Modern Radar, Wiley, NY, 1965; see p. 296.

LINKS

David W. Wilson, Table of n, a(n) for n = 1..400

R. Church, Tables of irreducible polynomials for the first four prime moduli, Annals Math., 36 (1935), 198-209.

S. V, Duzhin and D. V. Pasechnik, Groups acting on necklaces and sandpile groups, 2014. See p. 92. - N. J. A. Sloane, Jun 30 2014

MATHEMATICA

Table[If[n==1, 2, EulerPhi[2^n-1]/n], {n, 1, 50}] (* Vladimir Joseph Stephan Orlovsky, Jan 24 2012 *)

PROG

(PARI) a(n)=if(n==1, 2, eulerphi(2^n-1)/n) \\ Hauke Worpel (thebigh(AT)outgun.com), Jun 10 2008

CROSSREFS

Cf. A058947, A011260 (with initial term 1).

Sequence in context: A054706 A334500 A081727 * A077014 A093655 A023140

Adjacent sequences:  A000017 A000018 A000019 * A000021 A000022 A000023

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified November 24 22:57 EST 2020. Contains 338616 sequences. (Running on oeis4.)