A285485 Number of (n+1)-extended Skolem sequences of order n.

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

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