This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A098692 Main diagonal of array in A098691. 2
 1, 2, 10, 78, 777, 9800, 149796, 2690420, 55555500, 1296871224, 33773107758, 970753545580, 30527491279005, 1042604500906800, 38430716820193144, 1520662246114589640, 64291516462902839175, 2892426397164199846860, 137970526315789473684210, 6955460736173788715925048, 369510689788116404049535299 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is the number of self-complementary n-bead primitive necklaces of n+1 colors (see Miller (1978)). - Petros Hadjicostas, Aug 21 2019 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..387 H. Meyn and W. Götz, Self-reciprocal polynomials over finite fields, Séminaire Lotharingien de Combinatoire, B21d (1989), 8 pp. R. L. Miller, Necklaces, symmetries and self-reciprocal polynomials, Discr. Math. 22 (1978), 25-33. FORMULA a(n) = ((n + 1)^n - 1)/(2*n) if n = 2^s (for s >= 1), and (1/(2*n)) * Sum_{d|n, d odd} mu(d) * (n + 1)^(n/d) otherwise. - Petros Hadjicostas, Aug 21 2019 MAPLE with(numtheory): a:= n-> `if`(n=2^ilog2(n) and n>1, (n+1)^n-1, add(mobius(d)*        (n+1)^(n/d), d=select(x-> x::odd, divisors(n))))/(2*n): seq(a(n), n=1..20);  # Alois P. Heinz, Aug 21 2019 CROSSREFS Cf. A098691. Sequence in context: A134980 A240599 A212381 * A300994 A307722 A138273 Adjacent sequences:  A098689 A098690 A098691 * A098693 A098694 A098695 KEYWORD nonn AUTHOR Ralf Stephan, Sep 21 2004 EXTENSIONS More terms by Petros Hadjicostas, Aug 21 2019 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 20 18:39 EDT 2019. Contains 328269 sequences. (Running on oeis4.)