simcoal: Simulate Beta-coalescents with varying population size
In phoscheit/LambdaSkyline: Demographic Analysis of Multifurcating Phylogenies

This function simulates the ancestral process of a sample of n lineages in a larger population which has size of order N and fluctuates according to pop_size. The simulation is based on the results of (Schweinsberg 2003) and relies on supercritical branching processes with heavy-tailed offspring distribution.

1	simcoal(n, alpha, N, pop_size)

`n`	Number of sampled lineages at present time
`alpha`	The parameter of the Beta(2-alpha,alpha)-coalescent
`N`	Scaling parameter of the population size
`pop_size`	Vector containing the population size factor (true population size at time i is pop_size[i]*N)