A084117 - OEIS

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.

%I #6 Mar 31 2012 21:04:35

%S 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,

%T 11,10,13,8,11,6,17,12,15,10,21,0,11,6,17,12,15,14,17,12,15,10,21,16,

%U 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

%N 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.

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

%F a(2n) = n - a(n). - _Ralf Stephan_, Oct 07 2003

%Y Cf. A085015.

%K easy,nonn

%O 0,7

%A _Roland Bacher_, Jun 18 2003