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A084117
Multiplicity of the factor (1+x+x^2) in the characteristic polynomial modulo 2 of the symmetric matrix with entries binomial(i+j,i), 0<=i,j<n.
0
0, 0, 1, 0, 1, 0, 3, 2, 3, 2, 5, 0, 3, 2, 5, 4, 5, 4, 7, 2, 5, 0, 11, 6, 9, 8, 11, 6, 9, 8, 11, 10, 11, 10, 13, 8, 11, 6, 17, 12, 15, 10, 21, 0, 11, 6, 17, 12, 15, 14, 17, 12, 15, 10, 21, 16, 19, 18, 21, 16, 19, 18, 21, 20, 21, 20, 23, 18, 21, 16, 27, 22, 25, 20, 31, 10, 21, 16, 27, 22, 25
OFFSET
0,7
REFERENCES
R. Bacher and R. Chapman, Symmetric Pascal matrices modulo p, European J. Combin. 25 (2004), no. 4, 459-473.
FORMULA
a(2n) = n - a(n). - Ralf Stephan, Oct 07 2003
CROSSREFS
Cf. A085015.
Sequence in context: A093489 A066919 A268714 * A116895 A134267 A249800
KEYWORD
easy,nonn
AUTHOR
Roland Bacher, Jun 18 2003
STATUS
approved