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A004076 Number of hooked Skolem sequences of order n. 1
0, 1, 2, 0, 0, 38, 124, 0, 0, 12808, 72648, 0, 0, 21878816, 168870048, 0, 0, 113071735648, 1105816948032, 0, 0, 1395701792232832 (list; graph; refs; listen; history; text; internal format)
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 * A013369 A013416 A156433

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

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Last modified January 26 17:34 EST 2020. Contains 331280 sequences. (Running on oeis4.)