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

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

Author

Roland Bacher, Jun 18 2003

Keywords

• easy
• nonn

References

• R. Bacher and R. Chapman, Symmetric Pascal matrices modulo p, European J. Combin. 25 (2004), no. 4, 459-473.

Crossrefs

Cf. A085015.

Formula

a(2n) = n - a(n). - Ralf Stephan, Oct 07 2003