        1     ||  c(n)  | |                        0                        |
 </pre><p>A is a tridiagonal matrix (a band matrix of bandwidth 3) of size N=n+1. The factorization algorithms (A=LU) can be simplified considerably because a large number of zeros appear in regular patterns. The Crout method has been used: 1) Solve LZ=B</p>
<pre>
 u(1,2) = A(1,2)/A(1,1)
 z(1)   = B(1)/l(11)</pre><pre> FOR i=2, ..., N-1
   l(i,i)   = A(i,i)-A(i,i-1)u(i-1,i)
   u(i,i+1) = a(i,i+1)/l(i,i)
   z(i)     = [B(i)-A(i,i-1