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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 (list; graph; refs; listen; history; text; internal format)
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. Francetić, E. Mendelsohn, A survey of Skolem-type sequences and Rosa's use of them, Math. Slovaca 59 (2009), pp. 39-76

Jeppe Winther Larsen, Counting the Skolem sequences using inclusion-exclusion

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

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Last modified September 26 09:15 EDT 2021. Contains 347664 sequences. (Running on oeis4.)