

A285485


Number of (n+1)extended Skolem sequences of order n.


0



0, 0, 2, 2, 0, 0, 44, 260, 0, 0, 33104, 203712, 0, 0, 75499696, 621309008, 0, 0, 492805156768, 5068810602400, 0, 0, 7346944632542720
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OFFSET

1,3


COMMENTS

Number of Rosa sequences of order n.
a(n) computed counting reflected solutions.


LINKS

Table of n, a(n) for n=1..23.
N. FrancetiÄ‡, E. Mendelsohn, A survey of Skolemtype sequences and Rosa's use of them, Math. Slovaca 59 (2009), pp. 3976
Jeppe Winther Larsen, Counting the Skolem sequences using inclusionexclusion
R. Rees, N. Shalaby, A. Sharary, Indecomposable Skolem and Rosa sequences


EXAMPLE

For n = 3, there are 2 solutions: 1 1 3 0 2 3 2 and 2 3 2 0 3 1 1.
For n = 4, there are 2 solutions: 1 1 3 4 0 3 2 4 2 and 2 4 2 3 0 4 3 1 1.


CROSSREFS

Cf. A004077, A004075
Sequence in context: A282441 A281988 A190389 * A176127 A087637 A052458
Adjacent sequences: A285482 A285483 A285484 * A285486 A285487 A285488


KEYWORD

nonn,more


AUTHOR

Fausto A. C. Cariboni, Apr 19 2017


EXTENSIONS

a(1)a(18) from Jeppe Winther Larsen (jwl(AT)itu.dk), Oct 12 2009
a(1)a(18) confirmed, a(19)a(22) from Fausto A. C. Cariboni, Apr 19 2017
a(23) from Fausto A. C. Cariboni, May 11 2017


STATUS

approved



