A140426 - OEIS

A140426

Number of multi-symmetric Steinhaus matrices of size n.

1, 1, 2, 1, 2, 2, 2, 2, 4, 2, 4, 4, 4, 4, 8, 4, 8, 8, 8, 8, 16, 8, 16, 16, 16, 16, 32, 16, 32, 32, 32, 32, 64, 32, 64, 64, 64, 64, 128, 64, 128, 128, 128, 128, 256, 128, 256, 256, 256, 256, 512, 256, 512, 512, 512, 512, 1024, 512, 1024, 1024, 1024, 1024, 2048, 1024, 2048, 2048, 2048, 2048, 4096, 2048

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OFFSET

0,3

COMMENTS

Theorem 3.7, p. 9, of Chappelon.

LINKS

Table of n, a(n) for n=0..69.

Jonathan Chappelon, Regular Steinhaus graphs of odd degree, arXiv:0806.2779 [math.CO], 2008-2009.

Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,2)

FORMULA

a(n) = 2^ceiling(n/6) for n even, 2^ceiling((n-3)/6) for n odd.

G.f.: ( -1-x-2*x^2-x^3-2*x^4-2*x^5 ) / ( -1+2*x^6 ). - R. J. Mathar, Jan 22 2011