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A069925 a(n) = phi(2^n+1)/(2*n). 0
1, 1, 1, 2, 2, 4, 6, 16, 18, 40, 62, 160, 210, 448, 660, 2048, 2570, 5184, 9198, 24672, 32508, 76032, 121574, 344064, 405000, 1005888, 1569780, 4511520, 6066336, 12672000, 23091222, 67004160, 85342752, 200422656, 289531200, 892477440 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Number of primitive self-reciprocal polynomials of degree 2*n over GF(2). - Joerg Arndt, Jul 04 2012

LINKS

Table of n, a(n) for n=1..36.

Joerg Arndt, Matters Computational (The Fxtbook), section 40.8 "Self-reciprocal polynomials", pp. 846-484.

Helmut Meyn and Werner Götz, Self-reciprocal Polynomials Over Finite Fields, Séminaire Lotharingien de Combinatoire, B21d, pp.82-90, 1989.

FORMULA

a(n) = phi(2^n+1)/(2*n).

MATHEMATICA

Table[EulerPhi[2^n+1]/(2n), {n, 50}] (* Harvey P. Dale, Nov 15 2011 *)

PROG

(PARI) a(n) = eulerphi(2^n+1)/(2*n); /* Joerg Arndt, Jul 04 2012 */

CROSSREFS

Cf. A011260 (degree-n primitive polynomials).

Cf. A000048 (degree-2*n irreducible self-reciprocal polynomials).

Sequence in context: A116637 A153961 A134041 * A227315 A080611 A171421

Adjacent sequences:  A069922 A069923 A069924 * A069926 A069927 A069928

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Apr 25 2002

STATUS

approved

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Last modified August 21 02:25 EDT 2017. Contains 290855 sequences.