1,2

a(n)/a(n-1) tends to 3, an eigenvalue of the matrix.

Mathworld (Projective plane).

Let X = the 7x7 incidence matrix of the Fano plane PG(2,2): [1,1,1,0,0,0,0; 1,0,0,1,1,0,0; 1,0,0,0,0,1,1; 0,1,0,1,0,1,0; 0,1,0,0,1,0,1; 0,0,1,1,0,0,1; 0,0,1,0,1,1,0]. a(n) = the upper left term in X^n.

a(5) = 37, the upper left term of X^5.

Sequence in context: A089485 A146212 A018516 this_sequence A148503 A145939 A161703

Adjacent sequences: A138014 A138015 A138016 this_sequence A138018 A138019 A138020

nonn

Gary W. Adamson (qntmpkt(AT)yahoo.com), Feb 28 2008