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A001111 Number of inequivalent Hadamard designs of order 4n. 1
1, 1, 1, 5, 6, 1106, 208310, 10374196953 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

In other words, number of 2-(4*n-1,2*n-1,n-1) symmetric designs.

REFERENCES

Spence, Edward; Classification of Hadamard matrices of order 24 and 28. Discrete Math. 140 (1995), no. 1-3, 185-243.

LINKS

Table of n, a(n) for n=1..8.

R. K. Guy, Letters to N. J. A. Sloane, June-August 1968

Spence, Edward; Hadamard matrices

Index entries for sequences related to Hadamard matrices

CROSSREFS

Sequence in context: A246307 A269588 A048658 * A133079 A116916 A080332

Adjacent sequences:  A001108 A001109 A001110 * A001112 A001113 A001114

KEYWORD

nonn,hard,nice,more

AUTHOR

N. J. A. Sloane.

EXTENSIONS

a(8) from Brendan McKay, Feb 11 2012

STATUS

approved

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Last modified February 24 03:21 EST 2018. Contains 299595 sequences. (Running on oeis4.)