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A069925 a(n) = phi(2^n+1)/(2*n). 2
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
Joerg Arndt, Matters Computational (The Fxtbook), section 40.8 "Self-reciprocal polynomials", pp. 846-848.
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).
a(n) = A053285(n)/(2*n). - Amiram Eldar, Jun 02 2022
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: A153961 A134041 A358366 * A357951 A227315 A080611
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 25 2002
STATUS
approved

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Last modified June 14 08:24 EDT 2024. Contains 373393 sequences. (Running on oeis4.)