1,3

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

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.

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

P. Fan and M. Darnell, Sequence Design for Communications Applications, Wiley, NY, 1996, Table 5.1, p. 118.

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.

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

Joerg Arndt, Fxtbook

P. Koopman, Complete lists up to N=32

F. Ruskey, Primitive and Irreducible Polynomials

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

with(numtheory): phi(2^n-1)/n;

Table[EulerPhi[(2^n - 1)]/n, {n, 1, 50}]

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

See A058947 for initial terms. Cf. A001037, A000020.

Cf. A027695.

Sequence in context: A034422 A140833 A071908 this_sequence A117855 A086442 A071407

Adjacent sequences: A011257 A011258 A011259 this_sequence A011261 A011262 A011263

nonn,easy,nice

N. J. A. Sloane (njas(AT)research.att.com).