# Definition talk:Normal Series/Length

The length of $\left[{0 \,.\,.\, n}\right]$ does appear to be $n+1$ to me; is something glossed over in the definition or is this a plain flaw? --Lord_Farin (talk) 07:35, 8 October 2012 (UTC)
There are $n$ subgroups between $0$ and $n$ because the $n$th is not a subgroup, it's the group of which $G_{n-1}$ is a subgroup of. Hence the definition as the number of subgroups. Unless I'm missing something - the source work (Clark) which refers to the "length" does not explicitly define it, just refers to two different series having the same length. --prime mover (talk) 10:13, 8 October 2012 (UTC)
Apologies for not including the third option: LF is ignorant. The $n$ thus refers to the number of triangles. --Lord_Farin (talk) 10:16, 8 October 2012 (UTC)