# File diffeq.rb, line 136
def att(m,a,b,j)
ret = $zero
if (j <= m) then
ma = m + 2
i = j
while (i <= m)  do 
l = ma - i
al = (l - 1)
ret += a[i]*b[l]*ap_int(al)
i += 1
end
ret = ret / ap_int(m)
end
return (ret)
end