had_ehlich {HadamardR}

had_ehlich

Description

had_ehlich performs the construction of Hadamard matrix by Ehlich method

Usage

had_ehlich(x)

Arguments

x

Integer (order of the Hadamard matrix)

Details

Ehlich (1965)'s construction method requires order of the Hadamard matrix must be a of the form (n-1)^2. Conditions are (i)Order=(n-1)^2; (ii) n is a prime or prime power and 3(mod 4); (iii) (n-2) must be a prime or prime power. In case, if all the three conditions are satisfied,then function will return Hadamard matrix of order x otherwise NULL.

Value

Hadamard matrix of order x

References

Ehlich, H. (1965). Neue Hadamard-matrizen. Arch. Math., 16, 34-36.

Examples

had_ehlich(36)
had_ehlich(20)
#NULL