A004076 Number of hooked Skolem sequences of order n.

0, 1, 2, 0, 0, 38, 124, 0, 0, 12808, 72648, 0, 0, 21878816, 168870048, 0, 0, 113071735648, 1105816948032, 0, 0, 1395701792232832

Offset

1,3

References

CRC Handbook of Combinatorial Designs, 1996, p. 460.

Links

Table of n, a(n) for n=1..22.

Jeppe Winther Larsen, Counting the Skolem sequences using inclusion-exclusion, 2009

Example

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

Crossrefs

Sequence in context: A073111 A229685 A230469 * A365974 A013369 A013416

Adjacent sequences: A004073 A004074 A004075 * A004077 A004078 A004079

Keyword

nonn,more

Author

N. J. A. Sloane

Extensions

a(15)-a(18) from Jeppe Winther Larsen (jwl(AT)itu.dk), Oct 12 2009

a(4)-a(18) confirmed, a(3) corrected by Fausto A. C. Cariboni, Apr 11 2017

a(19)-a(22) from Fausto A. C. Cariboni, Apr 25 2017

Status

approved