For most regular coins the premine amount/blockreward structure can bee seen through github/src/main.cpp and searching for the word "nsubsidy".

For example:

https://github.com/PIVX-Project/PIVX/blob/master/src/main.cpp#L1617

nHeight is the block number and subsidy is the blockreward.

So if you see this:

    if (nHeight == 0) {
        nSubsidy = 60001 * COIN;

That means that there's a 60001 premine at block 1 (0).