√(n² + n) = [n;2,2n]

√d = n + (√d - n) mit d = n² + n

a0 = n

    1          1      (√d + n)   (√d + n)   2n + (√d - n)       (√d - n)
-------- = -------- × -------- = -------- = ------------- = 2 + --------
(√d - n)   (√d - n)   (√d + n)       n            n                 n

a1 = 2

    n          n      (√d + n)   n × (√d + n)   2n + (√d - n)        (√d - n)
-------- = -------- × -------- = ------------ = ------------- = 2n + --------
(√d - n)   (√d - n)   (√d + n)         n              1                  1

a2 = 2n